From nobody Fri Jul 24 14:46:23 2026 X-Original-To: dev-commits-src-all@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4h69mR64hzz6mFFn; Fri, 24 Jul 2026 14:46:31 +0000 (UTC) (envelope-from ronald-lists@klop.ws) Received: from smtp-relay-int-backup.realworks.nl (smtp-relay-int-backup.realworks.nl [87.255.56.188]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4h69mR2t2bz3RCK; Fri, 24 Jul 2026 14:46:31 +0000 (UTC) (envelope-from ronald-lists@klop.ws) Authentication-Results: mx1.freebsd.org; none Received: from smtp-relay-int.realworks.nl (rwvirtual373.colo.realworks.nl [10.0.10.73]) by mailrelayint1.colo2.realworks.nl (Postfix) with ESMTP id 4h69mJ0Tqzz5g; Fri, 24 Jul 2026 16:46:23 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=klop.ws; s=rw2; t=1784904384; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=w/ZYVvMbPx3/pFKCa3v2izmbkvmRjwncdv02LgdYpoQ=; b=BlW2Mc406gxs/UOeTQGJQNs2SZV/z0p/jmyxyWpYo+tR1W11JzquDI8t6cUAmFN97xXYzg ywPaCpurN36e/XRFAfg4V/qyD2nYXNK3F++LR8/sg8OZ1x84e1g7PmsiO/+UokPotioPAI dvszNphlQc0dyP60dbotGJ0f8TO2Rth5bbJuoRqNXFfDe5ARXwI+/XDDjgNp6e6swBcwK5 xGB6s9mjBpVAkNFs5iQ4hLC5EjdVy2oy/O5cFsjHLOzPSNjIDEPDZG262EMkMxAJK5WAlO 8xwkpNLr65eAAHIxWIM1hgOmdnD2At5MpzhxadXRX5QqOeltpOGjaZICkDgL0w== Received: from rwvirtual373.colo.realworks.nl (localhost [127.0.0.1]) by rwvirtual373.colo.realworks.nl (Postfix) with ESMTP id CE5B9140C0D; Fri, 24 Jul 2026 16:46:23 +0200 (CEST) Date: Fri, 24 Jul 2026 16:46:23 +0200 (CEST) From: Ronald Klop To: Christos Margiolis Cc: dev-commits-src-all@FreeBSD.org, src-committers@FreeBSD.org, Kevin Bowling , dev-commits-src-main@FreeBSD.org Message-ID: <20302724.1251.1784904383819@localhost> In-Reply-To: <6a636fb1.26412.26a07c1d@gitrepo.freebsd.org> References: <6a636fb1.26412.26a07c1d@gitrepo.freebsd.org> Subject: Re: git: 967e86d1ef2a - main - sound: Scale PCM secondary buffers by byte rate List-Id: Commit messages for all branches of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all List-Help: List-Post: List-Subscribe: List-Unsubscribe: X-BeenThere: dev-commits-src-all@freebsd.org Sender: owner-dev-commits-src-all@FreeBSD.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_1250_1540401911.1784904383741" X-Mailer: Realworks (805.141) X-Originating-Host: from (83-81-213-118.cable.dynamic.v4.ziggo.nl [83.81.213.118]) by rwvirtual373 [10.0.10.73] with HTTP; Fri, 24 Jul 2026 16:46:23 +0200 Importance: Normal X-Priority: 3 (Normal) X-Originating-User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:153.0) Gecko/20100101 Firefox/153.0 X-Rspamd-Queue-Id: 4h69mR2t2bz3RCK X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[]; ASN(0.00)[asn:38930, ipnet:87.255.32.0/19, country:NL] X-Spamd-Bar: ---- ------=_Part_1250_1540401911.1784904383741 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Is this a good candidate for Relnotes: yes in the commit message? Regards, Ronald. Van: Christos Margiolis Datum: vrijdag, 24 juli 2026 15:59 Aan: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org CC: Kevin Bowling Onderwerp: git: 967e86d1ef2a - main - sound: Scale PCM secondary buffers by byte rate > > The branch main has been updated by christos: > > URL: https://cgit.FreeBSD.org/src/commit/?id=967e86d1ef2ac8711c0ae7be353a9c08186f4e6f > > commit 967e86d1ef2ac8711c0ae7be353a9c08186f4e6f > Author: Kevin Bowling > AuthorDate: 2026-07-24 13:57:27 +0000 > Commit: Christos Margiolis > CommitDate: 2026-07-24 13:58:14 +0000 > > sound: Scale PCM secondary buffers by byte rate > > The fixed 128 KiB secondary buffer cap dates from stereo-sized streams. > High channel-count or high sample-width OSS streams can consume most of > that budget in one graph quantum, leaving too little room for capture > catch-up or playback headroom. > > Keep 128 KiB as the low-rate floor, but derive the effective soft-ring > cap from the channel byte rate, clamped to 4 MiB. Use that per-channel > cap when resizing the soft buffer and when clamping > SNDCTL_DSP_SETFRAGMENT requests. > > Also clamp SNDCTL_DSP_LOW_WATER to the current soft-buffer size so an > impossible readiness threshold cannot make poll/select wait forever. > > MFC after: 3 weeks > Reviewed by: christos > Differential Revision: https://reviews.freebsd.org/D58064 > --- > sys/dev/sound/pcm/channel.c | 62 +++++++++++++++++++++++++++++++++------------ > sys/dev/sound/pcm/channel.h | 30 +++++++++++++++++----- > sys/dev/sound/pcm/dsp.c | 38 +++++++++++++++++++-------- > 3 files changed, 96 insertions(+), 34 deletions(-) > > diff --git a/sys/dev/sound/pcm/channel.c b/sys/dev/sound/pcm/channel.c > index ff7620c772c3..21c223c61205 100644 > --- a/sys/dev/sound/pcm/channel.c > +++ b/sys/dev/sound/pcm/channel.c > @@ -1657,15 +1657,30 @@ round_pow2(u_int32_t v) > return ret; > } > > +u_int32_t > +chn_2ndbufmaxsize(struct pcm_channel *c) > +{ > + struct snd_dbuf *bs; > + uint64_t maxsize; > + > + CHN_LOCKASSERT(c); > + > + bs = c->bufsoft; > + maxsize = (uint64_t)bs->align * bs->spd * CHN_2NDBUFTIME_MS / 1000; > + RANGE(maxsize, CHN_2NDBUFSIZE_MIN, CHN_2NDBUFSIZE_MAX); > + > + return ((u_int32_t)maxsize); > +} > + > static u_int32_t > -round_blksz(u_int32_t v, int round) > +round_blksz(u_int32_t v, int round, u_int32_t maxsize) > { > u_int32_t ret, tmp; > > if (round < 1) > round = 1; > > - ret = min(round_pow2(v), CHN_2NDBUFMAXSIZE >> 1); > + ret = min(round_pow2(v), maxsize >> 1); > > if (ret > v && (ret >> 1) > 0 && (ret >> 1) >= ((v * 3) >> 2)) > ret >>= 1; > @@ -1780,14 +1795,16 @@ chn_calclatency(int dir, int latency, int bps, u_int32_t datarate, > if (latency < CHN_LATENCY_MIN || latency > CHN_LATENCY_MAX || > bps < 1 || datarate < 1 || > !(dir == PCMDIR_PLAY || dir == PCMDIR_REC)) { > + if (max < CHN_2NDBUFSIZE_MIN) > + max = CHN_2NDBUFSIZE_MIN; > if (rblksz != NULL) > - *rblksz = CHN_2NDBUFMAXSIZE >> 1; > + *rblksz = max >> 1; > if (rblkcnt != NULL) > *rblkcnt = 2; > printf("%s(): FAILED dir=%d latency=%d bps=%d " > "datarate=%u max=%u\n", > __func__, dir, latency, bps, datarate, max); > - return CHN_2NDBUFMAXSIZE; > + return max; > } > > lprofile = chn_latency_profile; > @@ -1804,7 +1821,7 @@ chn_calclatency(int dir, int latency, int bps, u_int32_t datarate, > datarate)); > if (bufsz > max) > bufsz = max; > - blksz = round_blksz(bufsz >> blkcnt, bps); > + blksz = round_blksz(bufsz >> blkcnt, bps, max); > > if (rblksz != NULL) > *rblksz = blksz; > @@ -1821,6 +1838,7 @@ chn_resizebuf(struct pcm_channel *c, int latency, > struct snd_dbuf *b, *bs, *pb; > int sblksz, sblkcnt, hblksz, hblkcnt, limit = 0, nsblksz, nsblkcnt; > int ret; > + u_int32_t maxsize; > > CHN_LOCKASSERT(c); > > @@ -1843,14 +1861,15 @@ chn_resizebuf(struct pcm_channel *c, int latency, > > bs = c->bufsoft; > b = c->bufhard; > + maxsize = chn_2ndbufmaxsize(c); > > if (!(blksz == 0 || blkcnt == -1) && > (blksz < 16 || blksz < bs->align || blkcnt < 2 || > - (blksz * blkcnt) > CHN_2NDBUFMAXSIZE)) > + (uint64_t)blksz * blkcnt > maxsize)) > return EINVAL; > > chn_calclatency(c->direction, latency, bs->align, > - bs->align * bs->spd, CHN_2NDBUFMAXSIZE, > + bs->align * bs->spd, maxsize, > &sblksz, &sblkcnt); > > if (blksz == 0 || blkcnt == -1) { > @@ -1871,7 +1890,7 @@ chn_resizebuf(struct pcm_channel *c, int latency, > * defeat the purpose of having custom control. The least > * we can do is round it to the nearest ^2 and align it. > */ > - sblksz = round_blksz(blksz, bs->align); > + sblksz = round_blksz(blksz, bs->align, maxsize); > sblkcnt = round_pow2(blkcnt); > } > > @@ -1890,18 +1909,28 @@ chn_resizebuf(struct pcm_channel *c, int latency, > sndbuf_xbytes(pb->blksz, pb, bs) * 2 : 0; > } > } else { > + /* > + * The byte-rate-scaled cap applies to the secondary buffer > + * only. It exists to absorb userland scheduling latency, > + * which the secondary buffer alone must cover; hardware > + * buffer geometry keeps the historical cap, since enlarging > + * it would change fragment sizes and interrupt cadence > + * visible to drivers, and remains bounded by b->maxsize > + * below. > + */ > hblkcnt = 2; > if (c->flags & CHN_F_HAS_SIZE) { > hblksz = round_blksz(sndbuf_xbytes(sblksz, bs, b), > - b->align); > + b->align, CHN_2NDBUFSIZE_MIN); > hblkcnt = round_pow2(bs->blkcnt); > } else > chn_calclatency(c->direction, latency, > b->align, b->align * b->spd, > - CHN_2NDBUFMAXSIZE, &hblksz, &hblkcnt); > + CHN_2NDBUFSIZE_MIN, &hblksz, &hblkcnt); > > if ((hblksz << 1) > b->maxsize) > - hblksz = round_blksz(b->maxsize >> 1, b->align); > + hblksz = round_blksz(b->maxsize >> 1, b->align, > + CHN_2NDBUFSIZE_MIN); > > while ((hblksz * hblkcnt) > b->maxsize) { > if (hblkcnt < 4) > @@ -1922,7 +1951,8 @@ chn_resizebuf(struct pcm_channel *c, int latency, > > if (!CHN_EMPTY(c, children)) { > nsblksz = round_blksz( > - sndbuf_xbytes(b->blksz, b, bs), bs->align); > + sndbuf_xbytes(b->blksz, b, bs), bs->align, > + maxsize); > nsblkcnt = b->blkcnt; > if (c->direction == PCMDIR_PLAY) { > do { > @@ -1938,13 +1968,13 @@ chn_resizebuf(struct pcm_channel *c, int latency, > limit = sndbuf_xbytes(b->blksz, b, bs) * 2; > } > > - if (limit > CHN_2NDBUFMAXSIZE) > - limit = CHN_2NDBUFMAXSIZE; > + if ((u_int32_t)limit > maxsize) > + limit = maxsize; > > - while ((sblksz * sblkcnt) < limit) > + while ((uint64_t)sblksz * sblkcnt < (uint64_t)limit) > sblkcnt <<= 1; > > - while ((sblksz * sblkcnt) > CHN_2NDBUFMAXSIZE) { > + while ((uint64_t)sblksz * sblkcnt > maxsize) { > if (sblkcnt < 4) > sblksz >>= 1; > else > diff --git a/sys/dev/sound/pcm/channel.h b/sys/dev/sound/pcm/channel.h > index c7f5bf93b8e5..c78c25dac13b 100644 > --- a/sys/dev/sound/pcm/channel.h > +++ b/sys/dev/sound/pcm/channel.h > @@ -430,15 +430,31 @@ enum { > #define CHN_TIMEOUT_MIN 1 > #define CHN_TIMEOUT_MAX 10 > > -/* > - * This should be large enough to hold all pcm data between > - * tsleeps in chn_{read,write} at the highest sample rate. > - * (which is usually 48kHz * 16bit * stereo = 192000 bytes/sec) > - */ > +/* Default block size for the secondary buffer. */ > #define CHN_2NDBUFBLKSIZE (2 * 1024) > /* The total number of blocks per secondary bufhard. */ > #define CHN_2NDBUFBLKNUM (32) > -/* The size of a whole secondary bufhard. */ > -#define CHN_2NDBUFMAXSIZE (131072) > +/* > + * The secondary buffer cap scales with the channel byte rate, targeting > + * CHN_2NDBUFTIME_MS of stream so that all pcm data between tsleeps in > + * chn_{read,write} fits, clamped to [CHN_2NDBUFSIZE_MIN, > + * CHN_2NDBUFSIZE_MAX]. > + * > + * The floor is the historical secondary buffer size and preserves memory > + * use for low byte-rate streams; it holds ~680 ms at the once-typical > + * 48kHz * 16bit * stereo rate (192000 bytes/sec), well above the target > + * (~38 KiB there). > + * > + * The ceiling bounds per-channel buffer memory. Buffers are allocated at > + * the derived size, so only streams that actually run at high byte rates > + * approach it. It holds the full target through MADI-class streams > + * (64ch * 32-bit * 48kHz, ~12.3 MB/s); beyond that, coverage shrinks > + * proportionally (e.g. ~85 ms at 64ch * 32-bit * 192kHz). > + */ > +#define CHN_2NDBUFSIZE_MIN (131072) > +#define CHN_2NDBUFSIZE_MAX (4 * 1024 * 1024) > +#define CHN_2NDBUFTIME_MS 200 > + > +u_int32_t chn_2ndbufmaxsize(struct pcm_channel *); > > #define CHANNEL_DECLARE(name) static DEFINE_CLASS(name, name ## _methods, sizeof(struct kobj)) > diff --git a/sys/dev/sound/pcm/dsp.c b/sys/dev/sound/pcm/dsp.c > index 0a5063410d24..f49df6e8a8c6 100644 > --- a/sys/dev/sound/pcm/dsp.c > +++ b/sys/dev/sound/pcm/dsp.c > @@ -109,6 +109,25 @@ static int dsp_oss_setsong(struct pcm_channel *wrch, struct pcm_channel *rdch, o > static int dsp_oss_setname(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_longname_t *name); > #endif > > +static uint32_t > +dsp_clamp_fragments(uint32_t maxfrags, uint32_t fragsz, uint32_t maxsize) > +{ > + if (maxfrags == 0) > + maxfrags = maxsize / fragsz; > + if (maxfrags < 2) > + maxfrags = 2; > + if ((uint64_t)maxfrags * fragsz > maxsize) > + maxfrags = maxsize / fragsz; > + return (maxfrags); > +} > + > +static unsigned int > +dsp_low_water(struct pcm_channel *ch, int lw) > +{ > + RANGE(lw, 1, ch->bufsoft->bufsize); > + return ((unsigned int)lw); > +} > + > int > dsp_make_dev(device_t dev) > { > @@ -1244,18 +1263,13 @@ dsp_ioctl(struct cdev *i_dev, u_long cmd, caddr_t arg, int mode, > RANGE(fragln, 4, 16); > fragsz = 1 << fragln; > > - if (maxfrags == 0) > - maxfrags = CHN_2NDBUFMAXSIZE / fragsz; > - if (maxfrags < 2) > - maxfrags = 2; > - if (maxfrags * fragsz > CHN_2NDBUFMAXSIZE) > - maxfrags = CHN_2NDBUFMAXSIZE / fragsz; > - > DEB(printf("SNDCTL_DSP_SETFRAGMENT %d frags, %d sz\n", maxfrags, fragsz)); > PCM_ACQUIRE_QUICK(d); > if (rdch) { > CHN_LOCK(rdch); > - ret = chn_setblocksize(rdch, maxfrags, fragsz); > + ret = chn_setblocksize(rdch, > + dsp_clamp_fragments(maxfrags, fragsz, > + chn_2ndbufmaxsize(rdch)), fragsz); > r_maxfrags = rdch->bufsoft->blkcnt; > r_fragsz = rdch->bufsoft->blksz; > CHN_UNLOCK(rdch); > @@ -1265,7 +1279,9 @@ dsp_ioctl(struct cdev *i_dev, u_long cmd, caddr_t arg, int mode, > } > if (wrch && ret == 0) { > CHN_LOCK(wrch); > - ret = chn_setblocksize(wrch, maxfrags, fragsz); > + ret = chn_setblocksize(wrch, > + dsp_clamp_fragments(maxfrags, fragsz, > + chn_2ndbufmaxsize(wrch)), fragsz); > maxfrags = wrch->bufsoft->blkcnt; > fragsz = wrch->bufsoft->blksz; > CHN_UNLOCK(wrch); > @@ -1653,12 +1669,12 @@ dsp_ioctl(struct cdev *i_dev, u_long cmd, caddr_t arg, int mode, > */ > if (wrch != NULL) { > CHN_LOCK(wrch); > - wrch->lw = (*arg_i > 1) ? *arg_i : 1; > + wrch->lw = dsp_low_water(wrch, *arg_i); > CHN_UNLOCK(wrch); > } > if (rdch != NULL) { > CHN_LOCK(rdch); > - rdch->lw = (*arg_i > 1) ? *arg_i : 1; > + rdch->lw = dsp_low_water(rdch, *arg_i); > CHN_UNLOCK(rdch); > } > break; > > > > ------=_Part_1250_1540401911.1784904383741 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Is this a good candidate for
Relnotes: yes
in the commit message?

Regards,
Ronald.


 

Van: Christos Margiolis <christos@FreeBSD.org>
Datum: vrijdag, 24 juli 2026 15:59
Aan: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org
CC: Kevin Bowling <kbowling@FreeBSD.org>
Onderwerp: git: 967e86d1ef2a - main - sound: Scale PCM secondary buffers by byte rate

The branch main has been updated by christos:

URL: https://cgit.FreeBSD.org/src/commit/?id=967e86d1ef2ac8711c0ae7be353a9c08186f4e6f

commit 967e86d1ef2ac8711c0ae7be353a9c08186f4e6f
Author:     Kevin Bowling <kbowling@FreeBSD.org>
AuthorDate: 2026-07-24 13:57:27 +0000
Commit:     Christos Margiolis <christos@FreeBSD.org>
CommitDate: 2026-07-24 13:58:14 +0000

    sound: Scale PCM secondary buffers by byte rate
    
    The fixed 128 KiB secondary buffer cap dates from stereo-sized streams.
    High channel-count or high sample-width OSS streams can consume most of
    that budget in one graph quantum, leaving too little room for capture
    catch-up or playback headroom.
    
    Keep 128 KiB as the low-rate floor, but derive the effective soft-ring
    cap from the channel byte rate, clamped to 4 MiB. Use that per-channel
    cap when resizing the soft buffer and when clamping
    SNDCTL_DSP_SETFRAGMENT requests.
    
    Also clamp SNDCTL_DSP_LOW_WATER to the current soft-buffer size so an
    impossible readiness threshold cannot make poll/select wait forever.
    
    MFC after:      3 weeks
    Reviewed by:    christos
    Differential Revision:  https://reviews.freebsd.org/D58064
---
 sys/dev/sound/pcm/channel.c | 62 +++++++++++++++++++++++++++++++++------------
 sys/dev/sound/pcm/channel.h | 30 +++++++++++++++++-----
 sys/dev/sound/pcm/dsp.c     | 38 +++++++++++++++++++--------
 3 files changed, 96 insertions(+), 34 deletions(-)

diff --git a/sys/dev/sound/pcm/channel.c b/sys/dev/sound/pcm/channel.c
index ff7620c772c3..21c223c61205 100644
--- a/sys/dev/sound/pcm/channel.c
+++ b/sys/dev/sound/pcm/channel.c
@@ -1657,15 +1657,30 @@ round_pow2(u_int32_t v)
    return ret;
 }
 
+u_int32_t
+chn_2ndbufmaxsize(struct pcm_channel *c)
+{
+   struct snd_dbuf *bs;
+   uint64_t maxsize;
+
+   CHN_LOCKASSERT(c);
+
+   bs = c->bufsoft;
+   maxsize = (uint64_t)bs->align * bs->spd * CHN_2NDBUFTIME_MS / 1000;
+   RANGE(maxsize, CHN_2NDBUFSIZE_MIN, CHN_2NDBUFSIZE_MAX);
+
+   return ((u_int32_t)maxsize);
+}
+
 static u_int32_t
-round_blksz(u_int32_t v, int round)
+round_blksz(u_int32_t v, int round, u_int32_t maxsize)
 {
    u_int32_t ret, tmp;
 
    if (round < 1)
        round = 1;
 
-   ret = min(round_pow2(v), CHN_2NDBUFMAXSIZE >> 1);
+   ret = min(round_pow2(v), maxsize >> 1);
 
    if (ret > v && (ret >> 1) > 0 && (ret >> 1) >= ((v * 3) >> 2))
        ret >>= 1;
@@ -1780,14 +1795,16 @@ chn_calclatency(int dir, int latency, int bps, u_int32_t datarate,
    if (latency < CHN_LATENCY_MIN || latency > CHN_LATENCY_MAX ||
        bps < 1 || datarate < 1 ||
        !(dir == PCMDIR_PLAY || dir == PCMDIR_REC)) {
+       if (max < CHN_2NDBUFSIZE_MIN)
+           max = CHN_2NDBUFSIZE_MIN;
        if (rblksz != NULL)
-           *rblksz = CHN_2NDBUFMAXSIZE >> 1;
+           *rblksz = max >> 1;
        if (rblkcnt != NULL)
            *rblkcnt = 2;
        printf("%s(): FAILED dir=%d latency=%d bps=%d "
            "datarate=%u max=%u\n",
            __func__, dir, latency, bps, datarate, max);
-       return CHN_2NDBUFMAXSIZE;
+       return max;
    }
 
    lprofile = chn_latency_profile;
@@ -1804,7 +1821,7 @@ chn_calclatency(int dir, int latency, int bps, u_int32_t datarate,
        datarate));
    if (bufsz > max)
        bufsz = max;
-   blksz = round_blksz(bufsz >> blkcnt, bps);
+   blksz = round_blksz(bufsz >> blkcnt, bps, max);
 
    if (rblksz != NULL)
        *rblksz = blksz;
@@ -1821,6 +1838,7 @@ chn_resizebuf(struct pcm_channel *c, int latency,
    struct snd_dbuf *b, *bs, *pb;
    int sblksz, sblkcnt, hblksz, hblkcnt, limit = 0, nsblksz, nsblkcnt;
    int ret;
+   u_int32_t maxsize;
 
    CHN_LOCKASSERT(c);
 
@@ -1843,14 +1861,15 @@ chn_resizebuf(struct pcm_channel *c, int latency,
 
    bs = c->bufsoft;
    b = c->bufhard;
+   maxsize = chn_2ndbufmaxsize(c);
 
    if (!(blksz == 0 || blkcnt == -1) &&
        (blksz < 16 || blksz < bs->align || blkcnt < 2 ||
-       (blksz * blkcnt) > CHN_2NDBUFMAXSIZE))
+       (uint64_t)blksz * blkcnt > maxsize))
        return EINVAL;
 
    chn_calclatency(c->direction, latency, bs->align,
-       bs->align * bs->spd, CHN_2NDBUFMAXSIZE,
+       bs->align * bs->spd, maxsize,
        &sblksz, &sblkcnt);
 
    if (blksz == 0 || blkcnt == -1) {
@@ -1871,7 +1890,7 @@ chn_resizebuf(struct pcm_channel *c, int latency,
         * defeat the purpose of having custom control. The least
         * we can do is round it to the nearest ^2 and align it.
         */
-       sblksz = round_blksz(blksz, bs->align);
+       sblksz = round_blksz(blksz, bs->align, maxsize);
        sblkcnt = round_pow2(blkcnt);
    }
 
@@ -1890,18 +1909,28 @@ chn_resizebuf(struct pcm_channel *c, int latency,
                sndbuf_xbytes(pb->blksz, pb, bs) * 2 : 0;
        }
    } else {
+       /*
+        * The byte-rate-scaled cap applies to the secondary buffer
+        * only.  It exists to absorb userland scheduling latency,
+        * which the secondary buffer alone must cover; hardware
+        * buffer geometry keeps the historical cap, since enlarging
+        * it would change fragment sizes and interrupt cadence
+        * visible to drivers, and remains bounded by b->maxsize
+        * below.
+        */
        hblkcnt = 2;
        if (c->flags & CHN_F_HAS_SIZE) {
            hblksz = round_blksz(sndbuf_xbytes(sblksz, bs, b),
-               b->align);
+               b->align, CHN_2NDBUFSIZE_MIN);
            hblkcnt = round_pow2(bs->blkcnt);
        } else
            chn_calclatency(c->direction, latency,
                b->align, b->align * b->spd,
-               CHN_2NDBUFMAXSIZE, &hblksz, &hblkcnt);
+               CHN_2NDBUFSIZE_MIN, &hblksz, &hblkcnt);
 
        if ((hblksz << 1) > b->maxsize)
-           hblksz = round_blksz(b->maxsize >> 1, b->align);
+           hblksz = round_blksz(b->maxsize >> 1, b->align,
+               CHN_2NDBUFSIZE_MIN);
 
        while ((hblksz * hblkcnt) > b->maxsize) {
            if (hblkcnt < 4)
@@ -1922,7 +1951,8 @@ chn_resizebuf(struct pcm_channel *c, int latency,
 
        if (!CHN_EMPTY(c, children)) {
            nsblksz = round_blksz(
-               sndbuf_xbytes(b->blksz, b, bs), bs->align);
+               sndbuf_xbytes(b->blksz, b, bs), bs->align,
+               maxsize);
            nsblkcnt = b->blkcnt;
            if (c->direction == PCMDIR_PLAY) {
                do {
@@ -1938,13 +1968,13 @@ chn_resizebuf(struct pcm_channel *c, int latency,
            limit = sndbuf_xbytes(b->blksz, b, bs) * 2;
    }
 
-   if (limit > CHN_2NDBUFMAXSIZE)
-       limit = CHN_2NDBUFMAXSIZE;
+   if ((u_int32_t)limit > maxsize)
+       limit = maxsize;
 
-   while ((sblksz * sblkcnt) < limit)
+   while ((uint64_t)sblksz * sblkcnt < (uint64_t)limit)
        sblkcnt <<= 1;
 
-   while ((sblksz * sblkcnt) > CHN_2NDBUFMAXSIZE) {
+   while ((uint64_t)sblksz * sblkcnt > maxsize) {
        if (sblkcnt < 4)
            sblksz >>= 1;
        else
diff --git a/sys/dev/sound/pcm/channel.h b/sys/dev/sound/pcm/channel.h
index c7f5bf93b8e5..c78c25dac13b 100644
--- a/sys/dev/sound/pcm/channel.h
+++ b/sys/dev/sound/pcm/channel.h
@@ -430,15 +430,31 @@ enum {
 #define CHN_TIMEOUT_MIN        1
 #define CHN_TIMEOUT_MAX        10
 
-/*
- * This should be large enough to hold all pcm data between
- * tsleeps in chn_{read,write} at the highest sample rate.
- * (which is usually 48kHz * 16bit * stereo = 192000 bytes/sec)
- */
+/* Default block size for the secondary buffer. */
 #define CHN_2NDBUFBLKSIZE  (2 * 1024)
 /* The total number of blocks per secondary bufhard. */
 #define CHN_2NDBUFBLKNUM   (32)
-/* The size of a whole secondary bufhard. */
-#define CHN_2NDBUFMAXSIZE  (131072)
+/*
+ * The secondary buffer cap scales with the channel byte rate, targeting
+ * CHN_2NDBUFTIME_MS of stream so that all pcm data between tsleeps in
+ * chn_{read,write} fits, clamped to [CHN_2NDBUFSIZE_MIN,
+ * CHN_2NDBUFSIZE_MAX].
+ *
+ * The floor is the historical secondary buffer size and preserves memory
+ * use for low byte-rate streams; it holds ~680 ms at the once-typical
+ * 48kHz * 16bit * stereo rate (192000 bytes/sec), well above the target
+ * (~38 KiB there).
+ *
+ * The ceiling bounds per-channel buffer memory.  Buffers are allocated at
+ * the derived size, so only streams that actually run at high byte rates
+ * approach it.  It holds the full target through MADI-class streams
+ * (64ch * 32-bit * 48kHz, ~12.3 MB/s); beyond that, coverage shrinks
+ * proportionally (e.g. ~85 ms at 64ch * 32-bit * 192kHz).
+ */
+#define CHN_2NDBUFSIZE_MIN (131072)
+#define CHN_2NDBUFSIZE_MAX (4 * 1024 * 1024)
+#define CHN_2NDBUFTIME_MS  200
+
+u_int32_t chn_2ndbufmaxsize(struct pcm_channel *);
 
 #define CHANNEL_DECLARE(name) static DEFINE_CLASS(name, name ## _methods, sizeof(struct kobj))
diff --git a/sys/dev/sound/pcm/dsp.c b/sys/dev/sound/pcm/dsp.c
index 0a5063410d24..f49df6e8a8c6 100644
--- a/sys/dev/sound/pcm/dsp.c
+++ b/sys/dev/sound/pcm/dsp.c
@@ -109,6 +109,25 @@ static int dsp_oss_setsong(struct pcm_channel *wrch, struct pcm_channel *rdch, o
 static int dsp_oss_setname(struct pcm_channel *wrch, struct pcm_channel *rdch, oss_longname_t *name);
 #endif
 
+static uint32_t
+dsp_clamp_fragments(uint32_t maxfrags, uint32_t fragsz, uint32_t maxsize)
+{
+   if (maxfrags == 0)
+       maxfrags = maxsize / fragsz;
+   if (maxfrags < 2)
+       maxfrags = 2;
+   if ((uint64_t)maxfrags * fragsz > maxsize)
+       maxfrags = maxsize / fragsz;
+   return (maxfrags);
+}
+
+static unsigned int
+dsp_low_water(struct pcm_channel *ch, int lw)
+{
+   RANGE(lw, 1, ch->bufsoft->bufsize);
+   return ((unsigned int)lw);
+}
+
 int
 dsp_make_dev(device_t dev)
 {
@@ -1244,18 +1263,13 @@ dsp_ioctl(struct cdev *i_dev, u_long cmd, caddr_t arg, int mode,
            RANGE(fragln, 4, 16);
            fragsz = 1 << fragln;
 
-           if (maxfrags == 0)
-               maxfrags = CHN_2NDBUFMAXSIZE / fragsz;
-           if (maxfrags < 2)
-               maxfrags = 2;
-           if (maxfrags * fragsz > CHN_2NDBUFMAXSIZE)
-               maxfrags = CHN_2NDBUFMAXSIZE / fragsz;
-
            DEB(printf("SNDCTL_DSP_SETFRAGMENT %d frags, %d sz\n", maxfrags, fragsz));
            PCM_ACQUIRE_QUICK(d);
                if (rdch) {
                CHN_LOCK(rdch);
-               ret = chn_setblocksize(rdch, maxfrags, fragsz);
+               ret = chn_setblocksize(rdch,
+                   dsp_clamp_fragments(maxfrags, fragsz,
+                   chn_2ndbufmaxsize(rdch)), fragsz);
                r_maxfrags = rdch->bufsoft->blkcnt;
                r_fragsz = rdch->bufsoft->blksz;
                CHN_UNLOCK(rdch);
@@ -1265,7 +1279,9 @@ dsp_ioctl(struct cdev *i_dev, u_long cmd, caddr_t arg, int mode,
            }
                if (wrch && ret == 0) {
                CHN_LOCK(wrch);
-               ret = chn_setblocksize(wrch, maxfrags, fragsz);
+               ret = chn_setblocksize(wrch,
+                   dsp_clamp_fragments(maxfrags, fragsz,
+                   chn_2ndbufmaxsize(wrch)), fragsz);
                maxfrags = wrch->bufsoft->blkcnt;
                fragsz = wrch->bufsoft->blksz;
                CHN_UNLOCK(wrch);
@@ -1653,12 +1669,12 @@ dsp_ioctl(struct cdev *i_dev, u_long cmd, caddr_t arg, int mode,
     */
        if (wrch != NULL) {
            CHN_LOCK(wrch);
-           wrch->lw = (*arg_i > 1) ? *arg_i : 1;
+           wrch->lw = dsp_low_water(wrch, *arg_i);
            CHN_UNLOCK(wrch);
        }
        if (rdch != NULL) {
            CHN_LOCK(rdch);
-           rdch->lw = (*arg_i > 1) ? *arg_i : 1;
+           rdch->lw = dsp_low_water(rdch, *arg_i);
            CHN_UNLOCK(rdch);
        }
        break;
 

  ------=_Part_1250_1540401911.1784904383741--