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From: | Yaodong Yang |
Subject: | Re: [Qemu-devel] questions about the bdrv_co_do_readv() |
Date: | Tue, 27 Aug 2013 17:55:26 -0500 |
I checked the argument, it looks like the same. I guess my confusion is the follows: code version: qemu-1.5.1 step 1: file: block-migration.c, function: static int mig_save_device_bulk(QEMUFile *f, BlkMigDevState *bmds) Inside this function, qemu calls the following function to read a chunk of data for migration. blk->aiocb = bdrv_aio_readv(bs, cur_sector, &blk->qiov, nr_sectors, blk_mig_read_cb, blk); my questions: No step 2: file block.c function: BlockDriverAIOCB *bdrv_aio_readv(BlockDriverState *bs, int64_t sector_num, QEMUIOVector *qiov, int nb_sectors, BlockDriverCompletionFunc *cb, void *opaque) my questions: No Step 3: file block.c function: static BlockDriverAIOCB *bdrv_co_aio_rw_vector(BlockDriverState *bs, int64_t sector_num, QEMUIOVector *qiov, int nb_sectors, BlockDriverCompletionFunc *cb, void *opaque, bool is_write) This function create a coroutine and then enter this coroutine. co = qemu_coroutine_create(bdrv_co_do_rw); qemu_coroutine_enter(co, acb); My questions: 1. What is the purpose of creating a coroutine here? Step 4: file: block.c function: static void coroutine_fn bdrv_co_do_rw(void *opaque) In this function, the bdrv_co_do_readv() is called. and After it, it create a bottom-half and then schedule this buttom half. acb->req.error = bdrv_co_do_readv(bs, acb->req.sector, acb->req.nb_sectors, acb->req.qiov, 0); My questions: 1. is the bdrv_co_do_readv function called within the IOthread or Migration thread? Step 5 file: block.c function: static void bdrv_co_em_bh(void *opaque) My questions: 1. Is this function called within the IOthread or Migration thread? In sum, I do not know clearly how the coroutine, bottom-half schemes are used for the migration job. is there any reference material related? Thanks a lot ! Yaodong it send s the bdrv_co_do_readv(block.c) function is exectued On Aug 27, 2013, at 2:45 AM, Stefan Hajnoczi <address@hidden> wrote: On Mon, Aug 26, 2013 at 09:59:51PM -0500, Yaodong Yang wrote:In sum, the bdrv_co_do_readv() seems to be executed inside two thread, the migration thread and native iothread. Both of them executed the function twice for a single request. Could someone explain it for me ? I appreciate it very much! |
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