Date: Fri, 30 Oct 2020 16:36:03 +0100 From: Mateusz Guzik <mjguzik@gmail.com> To: Mark Johnston <markj@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r367165 - head/sys/fs/tmpfs Message-ID: <CAGudoHHLQT-81Aa_XVPtR7BwAdbjZPNmz2G5EcggmR=uVg0a%2Bg@mail.gmail.com> In-Reply-To: <20201030145143.GB60293@raichu> References: <202010301407.09UE7Phw060731@repo.freebsd.org> <CAGudoHGBMFoeOKwZWq2%2B1xC9924Xi2AEt4a1zYgwa_EA3HzAkA@mail.gmail.com> <20201030145143.GB60293@raichu>
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On 10/30/20, Mark Johnston <markj@freebsd.org> wrote: > On Fri, Oct 30, 2020 at 03:08:32PM +0100, Mateusz Guzik wrote: >> On 10/30/20, Mateusz Guzik <mjg@freebsd.org> wrote: >> > Author: mjg >> > Date: Fri Oct 30 14:07:25 2020 >> > New Revision: 367165 >> > URL: https://svnweb.freebsd.org/changeset/base/367165 >> > >> > Log: >> > tmpfs: change tmpfs dirent zone into a malloc type >> > >> > It is 64 bytes. >> > >> >> Right now malloc has only power-of-2 zones but I'm looking into >> changing that. The allocator itself trivially extends to multiply of >> 16, but stat collection needs reworking. > > Sums of consecutive powers of 2 also works well. That is, 16, 16 + 8, > 32, 32 + 16, ... > > When I last looked I didn't see very many places that would benefit, at > least outside of ZFS. Probably the main one is CAM CCBs, and that'll be > helped by https://reviews.freebsd.org/D26844 . > I collected stats over part of make tinderbox, where they are rounded up to mulitplies of 8. (so size of 5 is 1, size of 32 is 4). There is huge demand for non-power-of-2 and a multiply of 16 is a conservative adjustment which wont require more than a few workloads to compare before/after. For example you can see a solid contingent of 9 (72 bytes) which right now is served from 128 byte zones. dtrace -n 'fbt::malloc:entry { @ = lquantize(arg0 % 8 ? ((arg0 / 8) * 8 + 1) : arg0 / 8, 0, 32, 1); }' value ------------- Distribution ------------- count 0 | 0 1 | 292436 2 | 140962 3 | 322732 4 |@@@@@ 12150230 5 | 686069 6 | 41067 7 |@ 2847728 8 |@@@ 6449825 9 |@@ 5794112 10 | 1107100 11 | 5913 12 | 15392 13 | 21885 14 | 1852 15 | 4100 16 | 5177 17 |@ 1833685 18 | 1541 19 | 1567 20 | 1189 21 | 809 22 | 7294 23 | 423 24 | 355 25 | 364280 26 | 450 27 | 416 28 | 444 29 | 193 30 | 83 31 | 188 >= 32 |@@@@@@@@@@@@@@@@@@@@@@@@@@ 61740786 -- Mateusz Guzik <mjguzik gmail.com>
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