From 355ee2d0e8ca536a6278c9c763ddd2f136eace3f Mon Sep 17 00:00:00 2001 From: Alberto Garcia Date: Tue, 4 Aug 2015 15:14:39 +0300 Subject: [PATCH] qcow2: mark the memory as no longer needed after qcow2_cache_empty() After having emptied the cache, the data in the cache tables is no longer useful, so we can tell the kernel that we are done with it. In Linux this frees the resources associated with it. The effect of this can be seen in the HMP commit operation: it moves data from the top to the base image (and fills both caches), then it empties the top image. At this point the data in that cache is no longer needed so it's just wasting memory. Signed-off-by: Alberto Garcia Reviewed-by: Max Reitz Message-id: 08538b098e1faf6c92496477cf9b47a20e5aacea.1438690126.git.berto@igalia.com Signed-off-by: Max Reitz --- block/qcow2-cache.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/block/qcow2-cache.c b/block/qcow2-cache.c index 53b8afc3d3..f63e7d8e70 100644 --- a/block/qcow2-cache.c +++ b/block/qcow2-cache.c @@ -22,8 +22,16 @@ * THE SOFTWARE. */ +/* Needed for CONFIG_MADVISE */ +#include "config-host.h" + +#if defined(CONFIG_MADVISE) || defined(CONFIG_POSIX_MADVISE) +#include +#endif + #include "block/block_int.h" #include "qemu-common.h" +#include "qemu/osdep.h" #include "qcow2.h" #include "trace.h" @@ -60,6 +68,22 @@ static inline int qcow2_cache_get_table_idx(BlockDriverState *bs, return idx; } +static void qcow2_cache_table_release(BlockDriverState *bs, Qcow2Cache *c, + int i, int num_tables) +{ +#if QEMU_MADV_DONTNEED != QEMU_MADV_INVALID + BDRVQcowState *s = bs->opaque; + void *t = qcow2_cache_get_table_addr(bs, c, i); + int align = getpagesize(); + size_t mem_size = (size_t) s->cluster_size * num_tables; + size_t offset = QEMU_ALIGN_UP((uintptr_t) t, align) - (uintptr_t) t; + size_t length = QEMU_ALIGN_DOWN(mem_size - offset, align); + if (length > 0) { + qemu_madvise((uint8_t *) t + offset, length, QEMU_MADV_DONTNEED); + } +#endif +} + Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables) { BDRVQcowState *s = bs->opaque; @@ -237,6 +261,8 @@ int qcow2_cache_empty(BlockDriverState *bs, Qcow2Cache *c) c->entries[i].lru_counter = 0; } + qcow2_cache_table_release(bs, c, 0, c->size); + c->lru_counter = 0; return 0; -- GitLab