Date: Mon, 27 Aug 2012 02:42:28 -0500 From: Alan Cox <alc@rice.edu> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: alc@freebsd.org, current@freebsd.org Subject: Re: less aggressive contigmalloc ? Message-ID: <503B24E4.6090701@rice.edu> In-Reply-To: <20120826171126.GA40672@onelab2.iet.unipi.it> References: <20120822120105.GA63763@onelab2.iet.unipi.it> <CAJUyCcPOte19TJXpCVAskhf%2BDia_Zg5uj6J_idW67rGsOLaZXw@mail.gmail.com> <20120823163145.GA3999@onelab2.iet.unipi.it> <50366398.2070700@rice.edu> <20120823174504.GB4820@onelab2.iet.unipi.it> <50371485.1020409@rice.edu> <20120824145708.GA16557@onelab2.iet.unipi.it> <5037A803.6030100@rice.edu> <20120824165428.GA17495@onelab2.iet.unipi.it> <5037B226.3000103@rice.edu> <20120826171126.GA40672@onelab2.iet.unipi.it>
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On 08/26/2012 12:11, Luigi Rizzo wrote: > On Fri, Aug 24, 2012 at 11:56:06AM -0500, Alan Cox wrote: >> On 08/24/2012 11:54, Luigi Rizzo wrote: >>> On Fri, Aug 24, 2012 at 11:12:51AM -0500, Alan Cox wrote: >>>> On 08/24/2012 09:57, Luigi Rizzo wrote: >>>>> On Fri, Aug 24, 2012 at 12:43:33AM -0500, Alan Cox wrote: >>>>>> On 08/23/2012 12:45, Luigi Rizzo wrote: >>>>>>> On Thu, Aug 23, 2012 at 12:08:40PM -0500, Alan Cox wrote: >>>>>>> ... >>>>>>>>> yes i do see that. >>>>>>>>> >>>>>>>>> Maybe less aggressive with M_NOWAIT but still kills processes. >>>>>>>> Are you compiling world with MALLOC_PRODUCTION? The latest version of >>>>>>> whatever the default is. But: >>>>>>> >>>>>>>> jemalloc uses significantly more memory when debugging options are >>>>>>>> enabled. This first came up in a thread titled "10-CURRENT and swap >>>>>>>> usage" back in June. >>>>>>>> >>>>>>>> Even at its most aggressive, M_WAITOK, contigmalloc() does not >>>>>>>> directly >>>>>>>> kill processes. If process death coincides with the use of >>>>>>>> contigmalloc(), then it is simply the result of earlier, successful >>>>>>>> contigmalloc() calls, or for that matter any other physical memory >>>>>>>> allocation calls, having depleted the pool of free pages to the point >>>>>>>> that the page daemon runs and invokes vm_pageout_oom(). >>>>>>> does it mean that those previous allocations relied on memory >>>>>>> overbooking ? >>>>>> Yes. >>>>>> >>>>>>> Is there a way to avoid that, then ? >>>>>> I believe that malloc()'s default minimum allocation size is 4MB. You >>>>>> could reduce that. >>>>>> >>>>>> Alternatively, you can enable MALLOC_PRODUCTION. >>>>> i tried this, and as others mentioned it makes life >>>>> better and reduces the problem but contigmalloc still triggers >>>>> random process kills. >>>> I would be curious to see a stack backtrace when vm_pageout_oom() is >>>> called. >>> you mean a backtrace of the process(es) that get killed ? >> No, a backtrace showing who called vm_pageout_oom(). Simply add a >> kdb_backtrace() call at the start of vm_pageout_oom(). There are two >> possibilities. I want to know which it is. > this is dmesg when I add kdb_backtrace() at the start of vm_pageout_oom() > The '... netmap_finalize_obj_allocator... are from my calls to > contigmalloc, each one doing one-page allocations. These calls are made with M_WAITOK? > I get 7-8 'KDB: stack backtrace' blocks, then allocations > restart successfully, then more failures... > The reference to fork_exit() does not seem right, because i am > in a block where i call contigmalloc, so the caller of > vm_pageout_grow_cache() should be kmem_alloc_contig(). Try this instead. At the start of vm_pageout_oom(), print the value of its parameter "shortage". That will uniquely identify the caller. > 630.004926 netmap_finalize_obj_allocator [593] cluster at 8910 ok > 630.005563 netmap_finalize_obj_allocator [593] cluster at 8912 ok > 630.006077 netmap_finalize_obj_allocator [593] cluster at 8914 ok > KDB: stack backtrace: > X_db_sym_numargs() at X_db_sym_numargs+0x1aa > vm_pageout_oom() at vm_pageout_oom+0x19 > vm_pageout_grow_cache() at vm_pageout_grow_cache+0xd01 > fork_exit() at fork_exit+0x11c > fork_trampoline() at fork_trampoline+0xe > --- trap 0, rip = 0, rsp = 0xffffff8005f12cb0, rbp = 0 --- > KDB: stack backtrace: > X_db_sym_numargs() at X_db_sym_numargs+0x1aa > vm_pageout_oom() at vm_pageout_oom+0x19 > vm_pageout_grow_cache() at vm_pageout_grow_cache+0xd01 > fork_exit() at fork_exit+0x11c > fork_trampoline() at fork_trampoline+0xe > --- trap 0, rip = 0, rsp = 0xffffff8005f12cb0, rbp = 0 --- > ... > > Some of the processes must be 'getty' because i also find > this line in dmesg: > > <118>Aug 26 16:47:11 init: getty repeating too quickly on port /dev/ttyv7, sleep > ing 30 secs > > cheers > luigi >
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