From: Tejun Heo <tj@kernel.org> To: Dave Chinner <david@fromorbit.com> Cc: Vivek Goyal <vgoyal@redhat.com>, Kent Overstreet <koverstreet@google.com>, Mikulas Patocka <mpatocka@redhat.com>, linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com, bharrosh@panasas.com, Jens Axboe <axboe@kernel.dk> Subject: Re: [PATCH v7 9/9] block: Avoid deadlocks with bio allocation by stacking drivers Date: Tue, 4 Sep 2012 21:37:37 -0700 [thread overview] Message-ID: <20120905043737.GA2737@mtj.dyndns.org> (raw) In-Reply-To: <20120905035758.GF13691@dastard> Hello, Dave. On Wed, Sep 05, 2012 at 01:57:59PM +1000, Dave Chinner wrote: > > But, yeah, this can't be solved by enlarging the stack size. The > > upper limit is unbound. > > Sure, but recursion issue is isolated to the block layer. > > If we can still submit IO directly through the block layer without > pushing it off to a work queue, then the overall stack usage problem > still exists. But if the block layer always pushes the IO off into > another workqueue to avoid stack overflows, then the context > switches are going to cause significant performance regressions for > high IOPS workloads. I don't really like either situation. Kent's proposed solution doesn't do that. The rescuer work item is used iff mempool allocation fails w/o GFP_WAIT. IOW, we're already under severe memory pressure and stalls are expected all around the kernel (somehow this sounds festive...) It doesn't alter the breadth-first walk of bio decomposition and shouldn't degrade performance in any noticeable way. > So while you are discussing stack issues, think a little about the > bigger picture outside of the immediate issue at hand - a better > solution for everyone might pop up.... It's probably because I haven't been bitten much from stack overflow but I'd like to keep thinking that stack overflows are extremely unusual and the ones causing them are the bad ones. Thank you very much. :p -- tejun
WARNING: multiple messages have this Message-ID (diff)
From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> To: Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org> Cc: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Kent Overstreet <koverstreet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Mikulas Patocka <mpatocka-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, bharrosh-C4P08NqkoRlBDgjK7y7TUQ@public.gmane.org, Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org> Subject: Re: [PATCH v7 9/9] block: Avoid deadlocks with bio allocation by stacking drivers Date: Tue, 4 Sep 2012 21:37:37 -0700 [thread overview] Message-ID: <20120905043737.GA2737@mtj.dyndns.org> (raw) In-Reply-To: <20120905035758.GF13691@dastard> Hello, Dave. On Wed, Sep 05, 2012 at 01:57:59PM +1000, Dave Chinner wrote: > > But, yeah, this can't be solved by enlarging the stack size. The > > upper limit is unbound. > > Sure, but recursion issue is isolated to the block layer. > > If we can still submit IO directly through the block layer without > pushing it off to a work queue, then the overall stack usage problem > still exists. But if the block layer always pushes the IO off into > another workqueue to avoid stack overflows, then the context > switches are going to cause significant performance regressions for > high IOPS workloads. I don't really like either situation. Kent's proposed solution doesn't do that. The rescuer work item is used iff mempool allocation fails w/o GFP_WAIT. IOW, we're already under severe memory pressure and stalls are expected all around the kernel (somehow this sounds festive...) It doesn't alter the breadth-first walk of bio decomposition and shouldn't degrade performance in any noticeable way. > So while you are discussing stack issues, think a little about the > bigger picture outside of the immediate issue at hand - a better > solution for everyone might pop up.... It's probably because I haven't been bitten much from stack overflow but I'd like to keep thinking that stack overflows are extremely unusual and the ones causing them are the bad ones. Thank you very much. :p -- tejun
next prev parent reply other threads:[~2012-09-05 4:37 UTC|newest] Thread overview: 128+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-08-28 17:37 [PATCH v7 0/9] Block cleanups, deadlock fix Kent Overstreet 2012-08-28 17:37 ` [PATCH v7 1/9] block: Generalized bio pool freeing Kent Overstreet 2012-08-28 17:37 ` Kent Overstreet 2012-08-28 17:37 ` [PATCH v7 2/9] dm: Use bioset's front_pad for dm_rq_clone_bio_info Kent Overstreet 2012-08-28 17:37 ` [PATCH v7 3/9] block: Add bio_reset() Kent Overstreet 2012-08-28 17:37 ` Kent Overstreet 2012-08-28 20:31 ` Tejun Heo 2012-08-28 20:31 ` Tejun Heo 2012-08-28 22:17 ` Kent Overstreet 2012-08-28 22:53 ` Kent Overstreet 2012-08-28 22:53 ` Kent Overstreet 2012-09-01 2:23 ` Tejun Heo 2012-09-01 2:23 ` Tejun Heo 2012-09-05 20:13 ` Kent Overstreet 2012-08-28 17:37 ` [PATCH v7 4/9] pktcdvd: Switch to bio_kmalloc() Kent Overstreet 2012-08-28 20:32 ` Tejun Heo 2012-08-28 20:32 ` Tejun Heo 2012-08-28 22:24 ` Kent Overstreet 2012-09-04 9:05 ` Jiri Kosina 2012-09-04 9:05 ` Jiri Kosina 2012-09-05 19:44 ` Kent Overstreet 2012-09-05 19:44 ` Kent Overstreet 2012-08-28 17:37 ` [PATCH v7 5/9] block: Kill bi_destructor Kent Overstreet 2012-08-28 20:36 ` Tejun Heo 2012-08-28 20:36 ` Tejun Heo 2012-08-28 22:07 ` Kent Overstreet 2012-08-28 17:37 ` [PATCH v7 6/9] block: Consolidate bio_alloc_bioset(), bio_kmalloc() Kent Overstreet 2012-08-28 17:37 ` Kent Overstreet 2012-08-28 20:41 ` Tejun Heo 2012-08-28 20:41 ` Tejun Heo 2012-08-28 22:03 ` Kent Overstreet 2012-08-28 22:03 ` Kent Overstreet 2012-09-01 2:17 ` Tejun Heo 2012-08-28 17:37 ` [PATCH v7 7/9] block: Add bio_clone_bioset(), bio_clone_kmalloc() Kent Overstreet 2012-08-28 20:44 ` Tejun Heo 2012-08-28 20:44 ` Tejun Heo 2012-08-28 22:05 ` Kent Overstreet 2012-09-01 2:19 ` Tejun Heo 2012-09-01 2:19 ` Tejun Heo 2012-08-28 17:37 ` [PATCH v7 8/9] block: Reorder struct bio_set Kent Overstreet 2012-08-28 17:37 ` [PATCH v7 9/9] block: Avoid deadlocks with bio allocation by stacking drivers Kent Overstreet 2012-08-28 20:49 ` Tejun Heo 2012-08-28 20:49 ` Tejun Heo 2012-08-28 22:28 ` Kent Overstreet 2012-08-28 23:01 ` Kent Overstreet 2012-08-28 23:01 ` Kent Overstreet 2012-08-29 1:31 ` Vivek Goyal 2012-08-29 1:31 ` Vivek Goyal 2012-08-29 3:25 ` Kent Overstreet 2012-08-29 12:57 ` Vivek Goyal 2012-08-29 12:57 ` Vivek Goyal 2012-08-29 14:39 ` [dm-devel] " Alasdair G Kergon 2012-08-29 14:39 ` Alasdair G Kergon 2012-08-29 16:26 ` Kent Overstreet 2012-08-29 16:26 ` Kent Overstreet 2012-08-29 21:01 ` John Stoffel 2012-08-29 21:08 ` Kent Overstreet 2012-08-29 21:08 ` Kent Overstreet 2012-08-28 22:06 ` Vivek Goyal 2012-08-28 22:06 ` Vivek Goyal 2012-08-28 22:23 ` Kent Overstreet 2012-08-28 22:23 ` Kent Overstreet 2012-08-29 16:24 ` Mikulas Patocka 2012-08-29 16:50 ` Kent Overstreet 2012-08-29 16:57 ` [dm-devel] " Alasdair G Kergon 2012-08-29 16:57 ` Alasdair G Kergon 2012-08-29 17:07 ` Vivek Goyal 2012-08-29 17:07 ` Vivek Goyal 2012-08-29 17:13 ` Kent Overstreet 2012-08-29 17:13 ` Kent Overstreet 2012-08-29 17:23 ` [dm-devel] " Alasdair G Kergon 2012-08-29 17:23 ` Alasdair G Kergon 2012-08-29 17:32 ` Kent Overstreet 2012-08-30 22:07 ` Vivek Goyal 2012-08-30 22:07 ` Vivek Goyal 2012-08-31 1:43 ` Kent Overstreet 2012-08-31 1:43 ` Kent Overstreet 2012-08-31 1:55 ` Kent Overstreet 2012-08-31 1:55 ` Kent Overstreet 2012-08-31 15:01 ` Vivek Goyal 2012-09-03 1:26 ` Kent Overstreet 2012-09-03 1:26 ` Kent Overstreet 2012-09-03 20:41 ` Mikulas Patocka 2012-09-03 20:41 ` Mikulas Patocka 2012-09-04 3:41 ` Kent Overstreet 2012-09-04 3:41 ` Kent Overstreet 2012-09-04 18:55 ` Tejun Heo 2012-09-04 18:55 ` Tejun Heo 2012-09-04 19:01 ` Tejun Heo 2012-09-04 19:43 ` Kent Overstreet 2012-09-04 19:43 ` Kent Overstreet 2012-09-04 19:42 ` Kent Overstreet 2012-09-04 21:03 ` Tejun Heo 2012-09-04 21:03 ` Tejun Heo 2012-09-04 19:26 ` Mikulas Patocka 2012-09-04 19:26 ` Mikulas Patocka 2012-09-04 19:39 ` Vivek Goyal 2012-09-04 19:39 ` Vivek Goyal 2012-09-04 19:51 ` [PATCH] dm: Use bioset's front_pad for dm_target_io Kent Overstreet 2012-09-04 19:51 ` Kent Overstreet 2012-09-04 21:20 ` Tejun Heo 2012-09-04 21:20 ` Tejun Heo 2012-09-11 19:28 ` [PATCH 2] " Mikulas Patocka 2012-09-11 19:28 ` Mikulas Patocka 2012-09-11 19:50 ` Kent Overstreet 2012-09-11 19:50 ` Kent Overstreet 2012-09-12 22:31 ` Mikulas Patocka 2012-09-12 22:31 ` Mikulas Patocka 2012-09-14 23:09 ` [dm-devel] " Alasdair G Kergon 2012-09-14 23:09 ` Alasdair G Kergon 2012-09-01 2:13 ` [PATCH v7 9/9] block: Avoid deadlocks with bio allocation by stacking drivers Tejun Heo 2012-09-01 2:13 ` Tejun Heo 2012-09-03 1:34 ` [PATCH v2] " Kent Overstreet 2012-09-03 1:34 ` Kent Overstreet 2012-09-04 15:00 ` [PATCH v7 9/9] " Vivek Goyal 2012-09-04 15:00 ` Vivek Goyal 2012-09-03 0:49 ` Dave Chinner 2012-09-03 0:49 ` Dave Chinner 2012-09-03 1:17 ` Kent Overstreet 2012-09-03 1:17 ` Kent Overstreet 2012-09-04 13:54 ` Vivek Goyal 2012-09-04 13:54 ` Vivek Goyal 2012-09-04 18:26 ` Tejun Heo 2012-09-04 18:26 ` Tejun Heo 2012-09-05 3:57 ` Dave Chinner 2012-09-05 3:57 ` Dave Chinner 2012-09-05 4:37 ` Tejun Heo [this message] 2012-09-05 4:37 ` Tejun Heo
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