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[78.12.229.84]) by smtp.gmail.com with ESMTPSA id l8sm2732271wmg.46.2018.01.12.03.32.13 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 12 Jan 2018 03:32:13 -0800 (PST) From: Paolo Bonzini To: qemu-devel@nongnu.org Date: Fri, 12 Jan 2018 12:31:11 +0100 Message-Id: <1515756676-3860-48-git-send-email-pbonzini@redhat.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1515756676-3860-1-git-send-email-pbonzini@redhat.com> References: <1515756676-3860-1-git-send-email-pbonzini@redhat.com> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2a00:1450:400c:c0c::243 Subject: [Qemu-devel] [PULL 47/52] find_ram_offset: Add comments and tracing X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Dr. David Alan Gilbert" Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" From: "Dr. David Alan Gilbert" Add some comments so I can understand the various nested loops. Add some tracing so I can see what they're doing. Signed-off-by: Dr. David Alan Gilbert Message-Id: <20180105170138.23357-2-dgilbert@redhat.com> Signed-off-by: Paolo Bonzini --- exec.c | 29 ++++++++++++++++++++++------- trace-events | 4 ++++ 2 files changed, 26 insertions(+), 7 deletions(-) diff --git a/exec.c b/exec.c index 4722e52..5e2fb55 100644 --- a/exec.c +++ b/exec.c @@ -1660,7 +1660,10 @@ static void *file_ram_alloc(RAMBlock *block, } #endif -/* Called with the ramlist lock held. */ +/* Allocate space within the ram_addr_t space that governs the + * dirty bitmaps. + * Called with the ramlist lock held. + */ static ram_addr_t find_ram_offset(ram_addr_t size) { RAMBlock *block, *next_block; @@ -1673,19 +1676,29 @@ static ram_addr_t find_ram_offset(ram_addr_t size) } RAMBLOCK_FOREACH(block) { - ram_addr_t end, next = RAM_ADDR_MAX; + ram_addr_t candidate, next = RAM_ADDR_MAX; - end = block->offset + block->max_length; + candidate = block->offset + block->max_length; + /* Search for the closest following block + * and find the gap. + */ RAMBLOCK_FOREACH(next_block) { - if (next_block->offset >= end) { + if (next_block->offset >= candidate) { next = MIN(next, next_block->offset); } } - if (next - end >= size && next - end < mingap) { - offset = end; - mingap = next - end; + + /* If it fits remember our place and remember the size + * of gap, but keep going so that we might find a smaller + * gap to fill so avoiding fragmentation. + */ + if (next - candidate >= size && next - candidate < mingap) { + offset = candidate; + mingap = next - candidate; } + + trace_find_ram_offset_loop(size, candidate, offset, next, mingap); } if (offset == RAM_ADDR_MAX) { @@ -1694,6 +1707,8 @@ static ram_addr_t find_ram_offset(ram_addr_t size) abort(); } + trace_find_ram_offset(size, offset); + return offset; } diff --git a/trace-events b/trace-events index 3695959..ec95e67 100644 --- a/trace-events +++ b/trace-events @@ -55,6 +55,10 @@ 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 +find_ram_offset(uint64_t size, uint64_t offset) "size: 0x%" PRIx64 " @ 0x%" PRIx64 +find_ram_offset_loop(uint64_t size, uint64_t candidate, uint64_t offset, uint64_t next, uint64_t mingap) "trying size: 0x%" PRIx64 " @ 0x%" PRIx64 ", offset: 0x%" PRIx64" next: 0x%" PRIx64 " mingap: 0x%" PRIx64 + # 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"