From: "Michael S. Tsirkin" <firstname.lastname@example.org> To: Avi Kivity <email@example.com> Cc: Sasha Levin <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org Subject: Re: [PATCH v3 2/2] virtio-ring: Allocate indirect buffers from cache when possible Date: Wed, 5 Sep 2012 17:27:57 +0300 [thread overview] Message-ID: <20120905142757.GA10925@redhat.com> (raw) In-Reply-To: <50475FD8.email@example.com> On Wed, Sep 05, 2012 at 05:21:12PM +0300, Avi Kivity wrote: > On 09/04/2012 09:41 PM, Michael S. Tsirkin wrote: > > On Tue, Sep 04, 2012 at 07:34:19PM +0300, Avi Kivity wrote: > >> On 08/31/2012 12:56 PM, Michael S. Tsirkin wrote: > >> > On Fri, Aug 31, 2012 at 11:36:07AM +0200, Sasha Levin wrote: > >> >> On 08/30/2012 03:38 PM, Michael S. Tsirkin wrote: > >> >> >> +static unsigned int indirect_alloc_thresh = 16; > >> >> > Why 16? Please make is MAX_SG + 1 this makes some sense. > >> >> > >> >> Wouldn't MAX_SG mean we always allocate from the cache? Isn't the memory waste > >> >> too big in this case? > >> > > >> > Sorry. I really meant MAX_SKB_FRAGS + 1. MAX_SKB_FRAGS is 17 so gets us > >> > threshold of 18. It is less than the size of an skb+shinfo itself so - > >> > does it look too big to you? Also why do you think 16 is not too big but > >> > 18 is? If there's a reason then I am fine with 16 too but then please > >> > put it in code comment near where the value is set. > >> > > >> > Yes this means virtio net always allocates from cache > >> > but this is a good thing, isn't it? Gets us more consistent > >> > performance. > >> > >> kmalloc() also goes to a cache. Is there a measurable difference? > > > > Yes see 0/2 and followup discussion. > > I don't see 0/2, looks like this was not threaded properly. What was > the subject line? My mistake, there is no 0/2, the resolts where in the followup thread of the previous version: [PATCH v2 2/2] virtio-ring: Allocate indirect buffers from cache when possible Sasha, could you please accompany the next version with a cover letter 0/2) including performance results? > > -- > error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2012-09-05 14:26 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-08-30 11:21 [PATCH v3 1/2] virtio-ring: Use threshold for switching to indirect descriptors Sasha Levin 2012-08-30 11:21 ` [PATCH v3 2/2] virtio-ring: Allocate indirect buffers from cache when possible Sasha Levin 2012-08-30 13:38 ` Michael S. Tsirkin 2012-08-31 9:36 ` Sasha Levin 2012-08-31 9:56 ` Michael S. Tsirkin 2012-09-04 16:34 ` Avi Kivity 2012-09-04 16:36 ` Avi Kivity 2012-09-04 18:41 ` Michael S. Tsirkin 2012-09-05 14:21 ` Avi Kivity 2012-09-05 14:27 ` Michael S. Tsirkin [this message] 2012-08-30 14:14 ` [PATCH v3 1/2] virtio-ring: Use threshold for switching to indirect descriptors Michael S. Tsirkin
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