|
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] xen/blkfront: increase the default value of xen_blkif_max_segments
On 17/12/14 16:13, Konrad Rzeszutek Wilk wrote: > On Wed, Dec 17, 2014 at 04:18:58PM +0800, Bob Liu wrote: >> >> On 12/16/2014 06:32 PM, Roger Pau Monné wrote: >>> 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 only have some results for 1M block size FIO test but I think that's >> enough. >> >> xen_blkfront.max Rate (MB/s) Percent of Dom-0 >> 32 11.1 31.0% >> 48 15.3 42.7% >> 64 19.8 55.3% >> 80 19.9 55.6% >> 96 23.0 64.2% >> 112 23.7 66.2% >> 128 31.6 88.3% >> >> The rates above are compared against the dom-0 rate of 35.8 MB/s. >> >>> 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 >> >> The number could be larger if using more pages as the >> xen-blkfront/backend ring based on Wei Liu's patch "xenbus_client: >> extend interface to suppurt multi-page ring", it helped improve the IO >> performance a lot on our system connected with high-end storage. >> I'm preparing resend related patches. > > Or potentially making the request and response be seperate rings - and the > response ring entries not tied in to the request. As in right now if we > have an request at say slot 1,5, and 7, we expect the response to be at > slot 1,5, and 7 as well. No. Responses are placed in the first available slot. The response is associated with the original request by the ID field. See make_response(). David _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
|
 |
Lists.xenproject.org is hosted with RackSpace, monitoring our |