From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
To: Roland Dreier <rdreier-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
Cc: Dan Carpenter <error27-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Roland Dreier <rolandd-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>,
Sean Hefty <sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
Hal Rosenstock
<hal.rosenstock-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
kernel-janitors-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [patch v4] infiniband: uverbs: handle large number of entries
Date: Wed, 24 Nov 2010 22:18:45 +0000 [thread overview]
Message-ID: <20101124221845.GH2369@obsidianresearch.com> (raw)
In-Reply-To: <adahbf6gytv.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
On Wed, Nov 24, 2010 at 02:07:40PM -0800, Roland Dreier wrote:
> - Fixing the potential integer overflow by capping cmd.ne at some high
> but safe value (1000 say)
This breaks how userspace wants to use poll, ie if you return anything
less than what I asked for then that means there is no more work to
do. Apps make this assumption, and is a reasonable thing to
do. Otherwise apps need a dummy call to ibv_poll to avoid races.
So if you are worried about how many times ib_poll_cq is called then
bound the kzalloc size and wrap the whole thing in a loop, but
realistically I have to think the performance trade off of
kzalloc/free vs calling ib_poll more often is not entirely obvious.
Who uses this path anyhow?
Jason
WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
To: Roland Dreier <rdreier-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
Cc: Dan Carpenter <error27-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Roland Dreier <rolandd-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>,
Sean Hefty <sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
Hal Rosenstock
<hal.rosenstock-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
kernel-janitors-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [patch v4] infiniband: uverbs: handle large number of entries
Date: Wed, 24 Nov 2010 15:18:45 -0700 [thread overview]
Message-ID: <20101124221845.GH2369@obsidianresearch.com> (raw)
In-Reply-To: <adahbf6gytv.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
On Wed, Nov 24, 2010 at 02:07:40PM -0800, Roland Dreier wrote:
> - Fixing the potential integer overflow by capping cmd.ne at some high
> but safe value (1000 say)
This breaks how userspace wants to use poll, ie if you return anything
less than what I asked for then that means there is no more work to
do. Apps make this assumption, and is a reasonable thing to
do. Otherwise apps need a dummy call to ibv_poll to avoid races.
So if you are worried about how many times ib_poll_cq is called then
bound the kzalloc size and wrap the whole thing in a loop, but
realistically I have to think the performance trade off of
kzalloc/free vs calling ib_poll more often is not entirely obvious.
Who uses this path anyhow?
Jason
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next prev parent reply other threads:[~2010-11-24 22:18 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-07 7:16 [patch] infiniband: uverbs: limit the number of entries Dan Carpenter
2010-10-07 7:16 ` Dan Carpenter
2010-10-07 16:16 ` Jason Gunthorpe
2010-10-07 16:16 ` Jason Gunthorpe
[not found] ` <20101007161649.GD21206-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2010-10-07 16:59 ` Dan Carpenter
2010-10-07 16:59 ` Dan Carpenter
2010-10-08 7:59 ` Nicolas Palix
2010-10-08 7:59 ` Nicolas Palix
[not found] ` <AANLkTin5zou2JHsdDyhGESuxyPonOs3kLo9Th0vg-kd8-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2010-10-08 14:25 ` [patch v2] " Dan Carpenter
2010-10-08 14:25 ` Dan Carpenter
2010-10-09 23:16 ` [patch] " Jason Gunthorpe
2010-10-09 23:16 ` Jason Gunthorpe
[not found] ` <20101009231607.GA24649-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2010-10-12 11:31 ` [patch v3] infiniband: uverbs: handle large " Dan Carpenter
2010-10-12 11:31 ` Dan Carpenter
2010-10-12 21:01 ` Jason Gunthorpe
2010-10-12 21:01 ` Jason Gunthorpe
[not found] ` <20101012210118.GR24268-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2010-10-13 9:05 ` Dan Carpenter
2010-10-13 9:05 ` Dan Carpenter
2010-10-13 9:13 ` [patch v4] " Dan Carpenter
2010-10-13 9:13 ` Dan Carpenter
2010-11-23 7:10 ` Dan Carpenter
2010-11-23 7:10 ` Dan Carpenter
2010-11-24 22:07 ` Roland Dreier
2010-11-24 22:07 ` Roland Dreier
[not found] ` <adahbf6gytv.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
2010-11-24 22:18 ` Jason Gunthorpe [this message]
2010-11-24 22:18 ` Jason Gunthorpe
[not found] ` <20101124221845.GH2369-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2010-11-25 4:05 ` Roland Dreier
2010-11-25 4:05 ` Roland Dreier
[not found] ` <adad3pugi90.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
2010-11-25 4:13 ` Jason Gunthorpe
2010-11-25 4:13 ` Jason Gunthorpe
[not found] ` <20101125041337.GA11049-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2010-11-25 15:00 ` ibv_post_send/recv kernel path optimizations (was: uverbs: handle large number of entries) Or Gerlitz
[not found] ` <4CEE7A22.2040706-smomgflXvOZWk0Htik3J/w@public.gmane.org>
2010-11-26 11:56 ` Walukiewicz, Miroslaw
[not found] ` <BE2BFE91933D1B4089447C644860408064B44854-IGOiFh9zz4wLt2AQoY/u9bfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2010-12-01 8:11 ` ibv_post_send/recv kernel path optimizations Or Gerlitz
[not found] ` <4CF60343.7050602-smomgflXvOZWk0Htik3J/w@public.gmane.org>
2010-12-08 12:14 ` Walukiewicz, Miroslaw
[not found] ` <BE2BFE91933D1B4089447C64486040806673CF38-IGOiFh9zz4wLt2AQoY/u9bfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2010-12-08 18:30 ` Jason Gunthorpe
2010-12-08 19:04 ` Roland Dreier
2010-12-14 14:12 ` Walukiewicz, Miroslaw
[not found] ` <BE2BFE91933D1B4089447C644860408066ABCF66-IGOiFh9zz4wLt2AQoY/u9bfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2010-12-14 18:17 ` Jason Gunthorpe
[not found] ` <20101214181735.GA2506-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2010-12-27 12:38 ` Or Gerlitz
[not found] ` <4D1888CB.2010101-hKgKHo2Ms0FWk0Htik3J/w@public.gmane.org>
2010-12-27 15:18 ` Walukiewicz, Miroslaw
[not found] ` <BE2BFE91933D1B4089447C644860408066C547E0-IGOiFh9zz4wLt2AQoY/u9bfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2010-12-27 15:22 ` Or Gerlitz
[not found] ` <4D18AF2D.1010109-smomgflXvOZWk0Htik3J/w@public.gmane.org>
2010-12-27 15:40 ` Walukiewicz, Miroslaw
2011-01-05 18:16 ` Roland Dreier
[not found] ` <ada4o9nfc6e.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
2011-01-10 14:15 ` Walukiewicz, Miroslaw
[not found] ` <BE2BFE91933D1B4089447C644860408066DDDF31-IGOiFh9zz4wLt2AQoY/u9bfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2011-01-10 20:38 ` Roland Dreier
[not found] ` <adawrmc7av2.fsf-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
2011-01-21 11:41 ` Walukiewicz, Miroslaw
[not found] ` <BE2BFE91933D1B4089447C644860408066F95285-IGOiFh9zz4wLt2AQoY/u9bfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2011-01-21 15:49 ` Hefty, Sean
[not found] ` <CF9C39F99A89134C9CF9C4CCB68B8DDF25C1D51C31-osO9UTpF0USkrb+BlOpmy7fspsVTdybXVpNB7YpNyf8@public.gmane.org>
2011-01-24 17:03 ` Walukiewicz, Miroslaw
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