On Wed, Sep 19, 2018 at 04:02:34PM +0000, Mateusz Guzik wrote: > Author: mjg > Date: Wed Sep 19 16:02:33 2018 > New Revision: 338802 > URL: https://svnweb.freebsd.org/changeset/base/338802 > > Log: > vm: check for empty kstack cache before locking > > The current cache logic checks the total number of stacks in the kernel, > which even on small boxes significantly exceeds the 128 limit (e.g. an > 8-way box with zfs has almost 800 stacks allocated). > > Stacks are cached earlier for each main thread. > > As a result the code is rarely executed, but when it is then (on boxes like > the above) it always fails. Since there are no provisions made for NUMA and > release time is approaching, just do a quick check to avoid acquiring the > lock. > > Approved by: re (kib) > > Modified: > head/sys/vm/vm_glue.c > > Modified: head/sys/vm/vm_glue.c > ============================================================================== > --- head/sys/vm/vm_glue.c Wed Sep 19 15:39:16 2018 (r338801) > +++ head/sys/vm/vm_glue.c Wed Sep 19 16:02:33 2018 (r338802) > @@ -327,7 +327,7 @@ vm_thread_new(struct thread *td, int pages) > else if (pages > KSTACK_MAX_PAGES) > pages = KSTACK_MAX_PAGES; > > - if (pages == kstack_pages) { > + if (pages == kstack_pages && kstack_cache != NULL) { > mtx_lock(&kstack_cache_mtx); > if (kstack_cache != NULL) { > ks_ce = kstack_cache;
Since kstack_cache is guaranteed not to be NULL, can the second conditional that checks for kstack_cache not being NULL be removed? Thanks, -- Shawn Webb Cofounder and Security Engineer HardenedBSD Tor-ified Signal: +1 443-546-8752 Tor+XMPP+OTR: latt...@is.a.hacker.sx GPG Key ID: 0x6A84658F52456EEE GPG Key Fingerprint: 2ABA B6BD EF6A F486 BE89 3D9E 6A84 658F 5245 6EEE
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