Messages in this thread | | | Date | Tue, 16 Dec 2014 11:32:31 +0100 | From | Roger Pau Monné <> | Subject | Re: [Xen-devel] [PATCH] xen/blkfront: increase the default value of xen_blkif_max_segments |
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El 16/12/14 a les 11.11, Bob Liu ha escrit: > The default maximum value of segments in indirect requests was 32, IO > operations with bigger block size(>32*4k) would be split and performance start > to drop. > > Nowadays backend device usually support 512k max_sectors_kb on desktop, and > may larger on server machines with high-end storage system. > The default size 128k was not very appropriate, this patch increases the default > maximum value to 128(128*4k=512k).
This looks fine, do you have any data/graphs to backup your reasoning?
I would also add to the commit message that this change implies we can now have 32*128+32 = 4128 in-flight grants, which greatly surpasses the default amount of persistent grants blkback can handle, so the LRU in blkback will kick in.
Roger.
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