Date: Fri, 25 Nov 2016 18:20:40 +0100 From: Fabien Thomas <fabient@freebsd.org> To: Mateusz Guzik <mjguzik@gmail.com> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r309143 - head/sys/libkern Message-ID: <4E934AF1-62E7-4C85-80D0-50548AD4E696@freebsd.org> In-Reply-To: <20161125160010.GA3307@dft-labs.eu> References: <201611251349.uAPDnX09042110@repo.freebsd.org> <20161125160010.GA3307@dft-labs.eu>
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> Le 25 nov. 2016 =C3=A0 17:00, Mateusz Guzik <mjguzik@gmail.com> a = =C3=A9crit : >=20 > On Fri, Nov 25, 2016 at 01:49:33PM +0000, Fabien Thomas wrote: >> Author: fabient >> Date: Fri Nov 25 13:49:33 2016 >> New Revision: 309143 >> URL: https://svnweb.freebsd.org/changeset/base/309143 >>=20 >> Log: >> In a dual processor system (2*6 cores) during IPSec throughput = tests, >> we see a lot of contention on the arc4 lock, used to generate the IV >> of the ESP output packets. >>=20 >> The idea of this patch is to split this mutex in order to reduce the >> contention on this lock. >>=20 >> +MALLOC_DEFINE(M_ARC4RANDOM, "arc4random", "arc4random structures"); >>=20 >> -static u_int8_t arc4_randbyte(void); >> +struct arc4_s { >> + u_int8_t i, j; >> + int numruns; >> + u_int8_t sbox[256]; >> + time_t t_reseed; >> + >> + struct mtx mtx; >> +}; >> + >=20 > Why is the lock at the end? Right now you got false sharing with the > next entry. >=20 > That said, I suggest: > 1. moving thelock to the beginning > 2. annotating the struct with __aligned(CACHE_LINE_SIZE) Yes good catch, it will be better that way. Committed as r309146. Thanks >=20 > --=20 > Mateusz Guzik <mjguzik gmail.com>
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