From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52036) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dkxnD-0001i7-Js for qemu-devel@nongnu.org; Thu, 24 Aug 2017 15:27:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dkxnC-0004BT-Kn for qemu-devel@nongnu.org; Thu, 24 Aug 2017 15:27:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10831) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dkxnC-0004Aj-Bi for qemu-devel@nongnu.org; Thu, 24 Aug 2017 15:27:50 -0400 From: "Dr. David Alan Gilbert (git)" Date: Thu, 24 Aug 2017 20:27:01 +0100 Message-Id: <20170824192730.8440-4-dgilbert@redhat.com> In-Reply-To: <20170824192730.8440-1-dgilbert@redhat.com> References: <20170824192730.8440-1-dgilbert@redhat.com> Subject: [Qemu-devel] [RFC v2 03/32] migrate: Update ram_block_discard_range for shared List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, maxime.coquelin@redhat.com, a.perevalov@samsung.com, mst@redhat.com, marcandre.lureau@redhat.com Cc: quintela@redhat.com, peterx@redhat.com, lvivier@redhat.com, aarcange@redhat.com, felipe@nutanix.com From: "Dr. David Alan Gilbert" The choice of call to discard a block is getting more complicated for other cases. We use fallocate PUNCH_HOLE in any file cases; it works for both hugepage and for tmpfs. We use the DONTNEED for non-hugepage cases either where they're anonymous or where they're private. Care should be taken when trying other backing files. Signed-off-by: Dr. David Alan Gilbert --- exec.c | 35 ++++++++++++++++++++++++----------- trace-events | 3 +++ 2 files changed, 27 insertions(+), 11 deletions(-) diff --git a/exec.c b/exec.c index d20c34ca83..67df2909ce 100644 --- a/exec.c +++ b/exec.c @@ -3573,6 +3573,7 @@ int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length) } if ((start + length) <= rb->used_length) { + bool need_madvise, need_fallocate; uint8_t *host_endaddr = host_startaddr + length; if ((uintptr_t)host_endaddr & (rb->page_size - 1)) { error_report("ram_block_discard_range: Unaligned end address: %p", @@ -3582,23 +3583,35 @@ int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length) errno = ENOTSUP; /* If we are missing MADVISE etc */ - if (rb->page_size == qemu_host_page_size) { -#if defined(CONFIG_MADVISE) - /* Note: We need the madvise MADV_DONTNEED behaviour of definitely - * freeing the page. - */ - ret = madvise(host_startaddr, length, MADV_DONTNEED); -#endif - } else { - /* Huge page case - unfortunately it can't do DONTNEED, but - * it can do the equivalent by FALLOC_FL_PUNCH_HOLE in the - * huge page file. + /* The logic here is messy; + * madvise DONTNEED fails for hugepages + * fallocate works on hugepages and shmem + */ + need_madvise = (rb->page_size == qemu_host_page_size); + need_fallocate = rb->fd != -1; + if (need_fallocate) { + /* For a file, this causes the area of the file to be zero'd + * if read, and for hugetlbfs also causes it to be unmapped + * so a userfault will trigger. */ #ifdef CONFIG_FALLOCATE_PUNCH_HOLE ret = fallocate(rb->fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, start, length); #endif } + /* i.e. need madvise but skip it if the fallocate failed */ + if (need_madvise && (!need_fallocate || (ret == 0))) { + /* For normal RAM this causes it to be unmapped, + * for shared memory it causes the local mapping to disappear + * and to fall back on the file contents (which we just + * fallocate'd away). + */ +#if defined(CONFIG_MADVISE) + ret = madvise(host_startaddr, length, MADV_DONTNEED); +#endif + } + trace_ram_block_discard_range(rb->idstr, host_startaddr, + need_madvise, need_fallocate, ret); if (ret) { ret = -errno; error_report("ram_block_discard_range: Failed to discard range " diff --git a/trace-events b/trace-events index 1f50f56d9d..213ee34f89 100644 --- a/trace-events +++ b/trace-events @@ -55,6 +55,9 @@ dma_complete(void *dbs, int ret, void *cb) "dbs=%p ret=%d cb=%p" dma_blk_cb(void *dbs, int ret) "dbs=%p ret=%d" dma_map_wait(void *dbs) "dbs=%p" +# exec.c +ram_block_discard_range(const char *rbname, void *hva, bool need_madvise, bool need_fallocate, int ret) "%s@%p: madvise: %d fallocate: %d ret: %d" + # memory.c memory_region_ops_read(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u" memory_region_ops_write(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u" -- 2.13.5