From: Avi Kivity <email@example.com> To: "Michael S. Tsirkin" <firstname.lastname@example.org> Cc: Sasha Levin <email@example.com>, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Subject: Re: [PATCH v3 2/2] virtio-ring: Allocate indirect buffers from cache when possible Date: Tue, 04 Sep 2012 19:34:19 +0300 [thread overview] Message-ID: <50462D8B.firstname.lastname@example.org> (raw) In-Reply-To: <20120831095628.GB24244@redhat.com> 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? Ugh, there's an ugly loop in __find_general_cachep(), which really wants to be replaced with fls(). -- error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2012-09-04 16:34 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 [this message] 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 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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