On 01/08/13 16:18, Roger Pau Monné wrote: > On 01/08/13 14:30, David Vrabel wrote: >> On 01/08/13 13:08, Roger Pau Monne wrote: >>> Right now the maximum number of grant operations that can be batched >>> in a single request is BLKIF_MAX_SEGMENTS_PER_REQUEST (11). This was >>> OK before indirect descriptors because the maximum number of segments >>> in a request was 11, but with the introduction of indirect >>> descriptors the maximum number of segments in a request has been >>> increased past 11. >>> >>> The memory used by the structures that are passed in the hypercall was >>> allocated from the stack, but if we have to increase the size of the >>> array we can no longer use stack memory, so we have to pre-allocate >>> it. >>> >>> This patch increases the maximum size of batch grant operations and >>> replaces the use of stack memory with pre-allocated memory, that is >>> reserved when the blkback instance is initialized. >> [...] >>> --- a/drivers/block/xen-blkback/xenbus.c >>> +++ b/drivers/block/xen-blkback/xenbus.c >> [...] >>> @@ -148,6 +155,16 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid) >>> if (!req->indirect_pages[j]) >>> goto fail; >>> } >>> + req->map = kcalloc(GNT_OPERATIONS_SIZE, sizeof(req->map[0]), >>> GFP_KERNEL); >>> + if (!req->map) >>> + goto fail; >>> + req->unmap = kcalloc(GNT_OPERATIONS_SIZE, >>> sizeof(req->unmap[0]), GFP_KERNEL); >>> + if (!req->unmap) >>> + goto fail; >>> + req->pages_to_gnt = kcalloc(GNT_OPERATIONS_SIZE, >>> sizeof(req->pages_to_gnt[0]), >>> + GFP_KERNEL); >>> + if (!req->pages_to_gnt) >>> + goto fail; >> >> Do these need to be per-request? Or can they all share a common set of >> arrays? > > No, we cannot share them unless we serialize the unmap of grants using a > spinlock (like we do when writing the reponse on the ring).
Any other comments on this one? Should I resubmit it? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
