From: Avi Kivity <firstname.lastname@example.org> To: "Michael S. Tsirkin" <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: Tue, 04 Sep 2012 19:36:05 +0300 [thread overview] Message-ID: <50462DF5.email@example.com> (raw) In-Reply-To: <50462D8B.firstname.lastname@example.org> On 09/04/2012 07:34 PM, 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? > > Ugh, there's an ugly loop in __find_general_cachep(), which really wants > to be replaced with fls(). > Actually, not, as the loop will be very short for small sizes. -- error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2012-09-04 16:36 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 [this message] 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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