Date: Mon, 3 Aug 2015 12:50:19 +0100 From: Steven Hartland <steven@multiplay.co.uk> To: Konstantin Belousov <kostikbel@gmail.com>, Peter Wemm <peter@wemm.org> Cc: svn-src-all@freebsd.org, Slawa Olhovchenkov <slw@zxy.spb.ru>, svn-src-head@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r286223 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs Message-ID: <55BF557B.60009@multiplay.co.uk> In-Reply-To: <20150803111942.GB2072@kib.kiev.ua> References: <201508030934.t739YAkT026668@repo.freebsd.org> <20150803094730.GA24698@zxy.spb.ru> <55BF431E.3020601@freebsd.org> <2757800.HIDNx1G49O@overcee.wemm.org> <20150803111942.GB2072@kib.kiev.ua>
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On 03/08/2015 12:19, Konstantin Belousov wrote: > On Mon, Aug 03, 2015 at 03:52:21AM -0700, Peter Wemm wrote: >> On Monday, August 03, 2015 11:31:58 AM Steven Hartland wrote: >>> On 03/08/2015 10:47, Slawa Olhovchenkov wrote: >>>> On Mon, Aug 03, 2015 at 09:34:10AM +0000, Steven Hartland wrote: >>>>> Author: smh >>>>> Date: Mon Aug 3 09:34:09 2015 >>>>> New Revision: 286223 >>>>> URL: https://svnweb.freebsd.org/changeset/base/286223 >>>>> >>>>> Log: >>>>> Fix KSTACK_PAGES check in ZFS module >>>>> >>>>> The check introduced by r285946 failed to add the dependency on >>>>> opt_kstack_pages.h which meant the default value for the platform >>>>> instead >>>>> of the customised options KSTACK_PAGES=X was being tested. >>>>> >>>>> Also wrap in #ifdef __FreeBSD__ for portability. >>>> /usr/src/sys/kern/kern_proc.c:int kstack_pages = KSTACK_PAGES; >>>> >>>> May be check variable kstack_pages is best way? >>>> Eliminate dependency on foreign opt_XXXX. >>> I did think of that but as other modules such as dtrace, which is also >>> cddl code, already have this dependency I went with this. >>> >>> I'm easy though, if there's a concusses that kstack_pages or possibly >>> curthread->td_kstack_pages, which would take into account the >>> possibility of varied thread stack sizes, then I can make that change. >>> >>> What do others think? >> The whole thing has missing the point. >> >> Changing the default for the entire kernel just because the zfs compat >> wrappers can't be bothered requesting a suitable value is.. unfortunate.. >> particularly when it is in freebsd-provided code, not upstream zfs code. >> >> Fix the kproc_kthread_add() calls in do_thread_create() and zvol_geom_run() >> instead. Enforce a lower bound there for zfs threads instead of making the >> entire rest of the kernel use more memory. >> >> eg: I'm thinking along these lines: >> Index: cddl/compat/opensolaris/sys/proc.h >> ==================================================== >> --- cddl/compat/opensolaris/sys/proc.h (revision 286224) >> +++ cddl/compat/opensolaris/sys/proc.h (working copy) >> @@ -77,6 +77,8 @@ >> ASSERT(state == TS_RUN); >> ASSERT(pp == &p0); >> >> + if (stksize < 16384) >> + stksize = 16384; /* Enforce lower bound on ZFS threads */ >> error = kproc_kthread_add(proc, arg, &zfsproc, &td, RFSTOPPED, >> stksize / PAGE_SIZE, "zfskern", "solthread %p", proc); >> if (error == 0) { >> >> >> Beware, some platforms have large pages (eg: ia64 in -stable has 8k, 16k or >> 32k pages, from memory). Specifying an arbitrary number of pages in code >> that's supposed to be portable isn't a good idea. > This would not help. Issue is the size of the thread0 stack, which > overflows in this case. > > I looked at the possibility of making default kernel stack size > configurable by a loader tunable, and the issue is that thread0 gets its > stack set up too early (locore for i386, hammer_time() for amd64). I.e., > it is possible to make the setting effective for all threads after thread0, > but not for the one which causes the issue. > > I do not want to modify ABI between loader and kernel to pass the parameter. I've created a review for the current proposed change to look at the kernel var kstack_pages vs the compile time define KSTACK_PAGES. For this change I don't want to get into fixing the thread0 stack size, which can be done later, just to provide a reasonable warning to the user that smaller values could cause a panic. @slw I've added peter and kib as reviewers if you phabricator account then feel free to add yourself. Regards Steve
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