Date: Mon, 09 May 2005 11:06:24 -0600 From: Scott Long <scottl@samsco.org> To: Ewan Todd <ewan@mathcode.net> Cc: freebsd-stable <freebsd-stable@freebsd.org> Subject: Re: Performance issue Message-ID: <427F9890.7010104@samsco.org> In-Reply-To: <20050509170316.GG281@mathcode.net> References: <20050509150018.GF281@mathcode.net> <427F8076.7030105@samsco.org> <20050509170316.GG281@mathcode.net>
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Ewan Todd wrote: >>>Whereas, the typical result for the new rig looked more like >>> >>> 105.36 real 71.10 user 33.41 sys >>> ... >>> 10548 involuntary context switches >>> >>> >> >>First of all, make sure that you have WITNESS and INVARIANTS off in your >>kernel. You might also want to recompile your kernel with the SMP >>option turned off. >> >>Scott > > > First of all, thanks to Mike Tancsa for suggesting 5.4 RC4 and to Pete > French for running the test independently on the higher spec machines > with 5.4 RC4 on them, confirming the system time thing, ruling out an > AMD problem, dissociating the system time result from the context > switching, and saving me the trouble of rediscovering the same problem > on 5.4 RC4. > > This is my first foray into the public world of FreeBSD discussion > lists, and I am encouraged by the helpfulness of the response. > > Scott, the 5.3 kernel I had was a essentially a GENERIC release > kernel, with about 100 options commented out. WITNESS and INVARIANTS > are off by default, which I confirmed by looking through `sysctl -a`. > However, I was curious to see what I would get if I switched them on, > so I added these options and recompiled the kernel: > > options KDB > options DDB > options INVARIANTS > options INVARIANT_SUPPORT > options WITNESS > options WITNESS_SKIPSPIN > > The result, below, has essentially the same user time (or just less, > if that makes any sense), but tripled system time. The context > switches are consistent with the one-per-10msec I saw before. Is > there anything useful I can do while I still have the kernel debug > options on? > > -e > > > 172.29 real 67.53 user 103.07 sys > 23376 maximum resident set size > 659 average shared memory size > 20805 average unshared data size > 127 average unshared stack size > 5402 page reclaims > 0 page faults > 0 swaps > 0 block input operations > 0 block output operations > 0 messages sent > 0 messages received > 0 signals received > 0 voluntary context switches > 17234 involuntary context switches > > 5.3 ships with SMP turned on, which makes lock operations rather expensive on single-processor machines. 4.x does not have SMP turned on by default. Would you be able to re-run your test with SMP turned off? Scott
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