[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] blkfront failure on migrate
On 22/11/12 13:46, Jan Beulich wrote: >>>> On 22.11.12 at 13:57, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote: >> In "Stage 1" as commented, we make a copy of the shadow map. We then >> reset the contents of the real shadow map, and selectively copy the >> in-use entries back from the copy to the real map. >> >> Looking at the code, it appears possible to do this rearranging inplace >> in the real shadow map, without requiring any memory allocation. >> >> Is this a sensible suggestion or have I overlooked something? This >> order-5 allocation is a disaster lying in wait for VMs with high memory >> pressure. > While merging the multi-page ring patches, I think I tried to make > this an in place copy operation, and it didn't work (don't recall > details though). This and/or the need to deal with shrinking ring > size across migration (maybe that was what really didn't work) > made me move stage 3 to kick_pending_request_queues(), and > allocate entries that actually need copying one by one, sticking > them on a list. > > Jan > Where are your multi-page ring patches? Are you saying this code is going to change very shortly? If the copy and copy back really cant be avoided, then making "sizeof(info->shadow)/PAGE_SIZE" allocations of order 0 would be substantially more friendly to environments with high memory pressure, at the cost of slightly more complicated indexing in the loop. -- Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer T: +44 (0)1223 225 900, http://www.citrix.com _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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