From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:47436) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gj2ls-0007H1-0u for qemu-devel@nongnu.org; Mon, 14 Jan 2019 08:59:21 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gj2lr-0004wp-1j for qemu-devel@nongnu.org; Mon, 14 Jan 2019 08:59:19 -0500 Received: from smtp03.citrix.com ([162.221.156.55]:1411) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gj2lq-0004wI-QQ for qemu-devel@nongnu.org; Mon, 14 Jan 2019 08:59:18 -0500 From: Anthony PERARD Date: Mon, 14 Jan 2019 13:51:54 +0000 Message-ID: <20190114135154.16826-26-anthony.perard@citrix.com> In-Reply-To: <20190114135154.16826-1-anthony.perard@citrix.com> References: <20190114135154.16826-1-anthony.perard@citrix.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain Subject: [Qemu-devel] [PULL 25/25] xen-block: avoid repeated memory allocation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: xen-devel@lists.xenproject.org, Peter Maydell , Anthony PERARD From: Tim Smith The xen-block dataplane currently allocates memory to hold the data for each request as that request is used, and frees it afterwards. Because it requires page-aligned blocks, this interacts poorly with non-page- aligned allocations and balloons the heap. Instead, allocate the maximum possible buffer size required for the protocol, which is BLKIF_MAX_SEGMENTS_PER_REQUEST (currently 11) pages when the request structure is created, and keep that buffer until it is destroyed. Since the requests are re-used via a free list, this should actually improve memory usage. Signed-off-by: Tim Smith Re-based and commit comment adjusted. Signed-off-by: Paul Durrant Acked-by: Anthony PERARD Signed-off-by: Anthony PERARD --- hw/block/dataplane/xen-block.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/hw/block/dataplane/xen-block.c b/hw/block/dataplane/xen-block.c index 35bfccfba7..d0d8905a33 100644 --- a/hw/block/dataplane/xen-block.c +++ b/hw/block/dataplane/xen-block.c @@ -70,7 +70,6 @@ static void reset_request(XenBlockRequest *request) memset(&request->req, 0, sizeof(request->req)); request->status = 0; request->start = 0; - request->buf = NULL; request->size = 0; request->presync = 0; @@ -95,6 +94,14 @@ static XenBlockRequest *xen_block_start_request(XenBlockDataPlane *dataplane) /* allocate new struct */ request = g_malloc0(sizeof(*request)); request->dataplane = dataplane; + /* + * We cannot need more pages per requests than this, and since we + * re-use requests, allocate the memory once here. It will be freed + * xen_block_dataplane_destroy() when the request list is freed. + */ + request->buf = qemu_memalign(XC_PAGE_SIZE, + BLKIF_MAX_SEGMENTS_PER_REQUEST * + XC_PAGE_SIZE); dataplane->requests_total++; qemu_iovec_init(&request->v, 1); } else { @@ -272,14 +279,12 @@ static void xen_block_complete_aio(void *opaque, int ret) if (ret == 0) { xen_block_copy_request(request); } - qemu_vfree(request->buf); break; case BLKIF_OP_WRITE: case BLKIF_OP_FLUSH_DISKCACHE: if (!request->req.nr_segments) { break; } - qemu_vfree(request->buf); break; default: break; @@ -360,12 +365,10 @@ static int xen_block_do_aio(XenBlockRequest *request) { XenBlockDataPlane *dataplane = request->dataplane; - request->buf = qemu_memalign(XC_PAGE_SIZE, request->size); if (request->req.nr_segments && (request->req.operation == BLKIF_OP_WRITE || request->req.operation == BLKIF_OP_FLUSH_DISKCACHE) && xen_block_copy_request(request)) { - qemu_vfree(request->buf); goto err; } @@ -665,6 +668,7 @@ void xen_block_dataplane_destroy(XenBlockDataPlane *dataplane) request = QLIST_FIRST(&dataplane->freelist); QLIST_REMOVE(request, list); qemu_iovec_destroy(&request->v); + qemu_vfree(request->buf); g_free(request); } -- Anthony PERARD