Date: Tue, 16 Nov 2021 18:52:43 GMT From: Mark Johnston <markj@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: fcaa890c4469 - main - mbuf: Only allow extpg mbufs if the system has a direct map Message-ID: <202111161852.1AGIqhxc017891@gitrepo.freebsd.org>
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The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=fcaa890c4469118255d463495b4044eef484fa3e commit fcaa890c4469118255d463495b4044eef484fa3e Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2021-11-16 18:31:04 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2021-11-16 18:31:04 +0000 mbuf: Only allow extpg mbufs if the system has a direct map Some upcoming changes will modify software checksum routines like in_cksum() to operate using m_apply(), which uses the direct map to access packet data for unmapped mbufs. This approach of course does not work on platforms without a direct map, so we have to disallow the use of unmapped mbufs on such platforms. I believe this is the right tradeoff: we only configure KTLS on amd64 and arm64 today (and one KTLS consumer, NFS TLS, requires a direct map already), and the use of unmapped mbufs with plain sendfile is a recent optimization. If need be, m_apply() could be modified to create CPU-private mappings of extpg mbuf pages as a fallback. So, change mb_use_ext_pgs to be hard-wired to zero on systems without a direct map. Note that PMAP_HAS_DMAP is not a compile-time constant on some systems, so the default value of mb_use_ext_pgs has to be determined during boot. Reviewed by: jhb Discussed with: gallatin MFC after: 2 weeks Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D32940 --- sys/kern/kern_mbuf.c | 32 ++++++++++++++++++++++++++++++-- sys/rpc/rpcsec_tls/rpctls_impl.c | 2 +- 2 files changed, 31 insertions(+), 3 deletions(-) diff --git a/sys/kern/kern_mbuf.c b/sys/kern/kern_mbuf.c index d1f2fd2bd9e4..78a270189a4b 100644 --- a/sys/kern/kern_mbuf.c +++ b/sys/kern/kern_mbuf.c @@ -116,9 +116,26 @@ int nmbjumbop; /* limits number of page size jumbo clusters */ int nmbjumbo9; /* limits number of 9k jumbo clusters */ int nmbjumbo16; /* limits number of 16k jumbo clusters */ -bool mb_use_ext_pgs = true; /* use M_EXTPG mbufs for sendfile & TLS */ -SYSCTL_BOOL(_kern_ipc, OID_AUTO, mb_use_ext_pgs, CTLFLAG_RWTUN, +bool mb_use_ext_pgs = false; /* use M_EXTPG mbufs for sendfile & TLS */ + +static int +sysctl_mb_use_ext_pgs(SYSCTL_HANDLER_ARGS) +{ + int error, extpg; + + extpg = mb_use_ext_pgs; + error = sysctl_handle_int(oidp, &extpg, 0, req); + if (error == 0 && req->newptr != NULL) { + if (extpg != 0 && !PMAP_HAS_DMAP) + error = EOPNOTSUPP; + else + mb_use_ext_pgs = extpg != 0; + } + return (error); +} +SYSCTL_PROC(_kern_ipc, OID_AUTO, mb_use_ext_pgs, CTLTYPE_INT | CTLFLAG_RW, &mb_use_ext_pgs, 0, + sysctl_mb_use_ext_pgs, "IU", "Use unmapped mbufs for sendfile(2) and TLS offload"); static quad_t maxmbufmem; /* overall real memory limit for all mbufs */ @@ -137,6 +154,7 @@ static void tunable_mbinit(void *dummy) { quad_t realmem; + int extpg; /* * The default limit for all mbuf related memory is 1/2 of all @@ -173,6 +191,16 @@ tunable_mbinit(void *dummy) if (nmbufs < nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16) nmbufs = lmax(maxmbufmem / MSIZE / 5, nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16); + + /* + * Unmapped mbufs can only safely be used on platforms with a direct + * map. + */ + if (PMAP_HAS_DMAP) { + extpg = mb_use_ext_pgs; + TUNABLE_INT_FETCH("kern.ipc.mb_use_ext_pgs", &extpg); + mb_use_ext_pgs = extpg != 0; + } } SYSINIT(tunable_mbinit, SI_SUB_KMEM, SI_ORDER_MIDDLE, tunable_mbinit, NULL); diff --git a/sys/rpc/rpcsec_tls/rpctls_impl.c b/sys/rpc/rpcsec_tls/rpctls_impl.c index 110ba107540a..c495213b08e2 100644 --- a/sys/rpc/rpcsec_tls/rpctls_impl.c +++ b/sys/rpc/rpcsec_tls/rpctls_impl.c @@ -711,7 +711,7 @@ rpctls_getinfo(u_int *maxlenp, bool rpctlscd_run, bool rpctlssd_run) int error; size_t siz; - if (PMAP_HAS_DMAP == 0 || !mb_use_ext_pgs) + if (!mb_use_ext_pgs) return (false); siz = sizeof(enable); error = kernel_sysctlbyname(curthread, "kern.ipc.tls.enable",
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