From: "Michael S. Tsirkin" <firstname.lastname@example.org> To: Sasha Levin <email@example.com> Cc: 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: Fri, 31 Aug 2012 12:56:28 +0300 [thread overview] Message-ID: <20120831095628.GB24244@redhat.com> (raw) In-Reply-To: <email@example.com> 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. -- MST
next prev parent reply other threads:[~2012-08-31 9:55 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 [this message] 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 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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