From: "Leonardo Brás" <leobras@redhat.com>
To: Juan Quintela <quintela@redhat.com>, qemu-devel@nongnu.org
Cc: "Marcel Apfelbaum" <marcel.apfelbaum@gmail.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
"Peter Xu" <peterx@redhat.com>, "Eric Blake" <eblake@redhat.com>,
"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
"Yanan Wang" <wangyanan55@huawei.com>,
"Markus Armbruster" <armbru@redhat.com>,
"Eduardo Habkost" <eduardo@habkost.net>
Subject: Re: [PATCH v7 11/12] multifd: Zero pages transmission
Date: Fri, 02 Sep 2022 10:27:32 -0300 [thread overview]
Message-ID: <a422638b88db67dc0bc26526578ee5be3880b6a8.camel@redhat.com> (raw)
In-Reply-To: <20220802063907.18882-12-quintela@redhat.com>
On Tue, 2022-08-02 at 08:39 +0200, Juan Quintela wrote:
> This implements the zero page dection and handling.
>
> Signed-off-by: Juan Quintela <quintela@redhat.com>
>
> ---
>
> Add comment for offset (dave)
> Use local variables for offset/block to have shorter lines
> ---
> migration/multifd.h | 5 +++++
> migration/multifd.c | 41 +++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 44 insertions(+), 2 deletions(-)
>
> diff --git a/migration/multifd.h b/migration/multifd.h
> index a1b852200d..5931de6f86 100644
> --- a/migration/multifd.h
> +++ b/migration/multifd.h
> @@ -52,6 +52,11 @@ typedef struct {
> uint32_t unused32[1]; /* Reserved for future use */
> uint64_t unused64[3]; /* Reserved for future use */
> char ramblock[256];
> + /*
> + * This array contains the pointers to:
> + * - normal pages (initial normal_pages entries)
> + * - zero pages (following zero_pages entries)
> + */
> uint64_t offset[];
> } __attribute__((packed)) MultiFDPacket_t;
>
> diff --git a/migration/multifd.c b/migration/multifd.c
> index 4473d9f834..89811619d8 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -11,6 +11,7 @@
> */
>
> #include "qemu/osdep.h"
> +#include "qemu/cutils.h"
> #include "qemu/rcu.h"
> #include "exec/target_page.h"
> #include "sysemu/sysemu.h"
> @@ -275,6 +276,12 @@ static void multifd_send_fill_packet(MultiFDSendParams *p)
>
> packet->offset[i] = cpu_to_be64(temp);
> }
> + for (i = 0; i < p->zero_num; i++) {
> + /* there are architectures where ram_addr_t is 32 bit */
> + uint64_t temp = p->zero[i];
> +
> + packet->offset[p->normal_num + i] = cpu_to_be64(temp);
> + }
> }
>
> static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
> @@ -358,6 +365,18 @@ static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
> p->normal[i] = offset;
> }
>
> + for (i = 0; i < p->zero_num; i++) {
> + uint64_t offset = be64_to_cpu(packet->offset[p->normal_num + i]);
> +
> + if (offset > (block->used_length - p->page_size)) {
> + error_setg(errp, "multifd: offset too long %" PRIu64
> + " (max " RAM_ADDR_FMT ")",
> + offset, block->used_length);
> + return -1;
> + }
> + p->zero[i] = offset;
> + }
> +
> return 0;
> }
IIUC ram_addr_t is supposed to be the address size for the architecture, mainly
being 32 or 64 bits. So packet->offset[i] is always u64, and p->zero[i] possibly
being u32 or u64.
Since both local variables and packet->offset[i] are 64-bit, there is no issue.
But on 'p->zero[i] = offset' we can have 'u32 = u64', and this should raise a
warning (or am I missing something?).
>
> @@ -648,6 +667,8 @@ static void *multifd_send_thread(void *opaque)
> {
> MultiFDSendParams *p = opaque;
> Error *local_err = NULL;
> + /* qemu older than 7.0 don't understand zero page on multifd channel */
> + bool use_zero_page = migrate_use_multifd_zero_page();
> int ret = 0;
> bool use_zero_copy_send = migrate_use_zero_copy_send();
>
> @@ -670,6 +691,7 @@ static void *multifd_send_thread(void *opaque)
> qemu_mutex_lock(&p->mutex);
>
> if (p->pending_job) {
> + RAMBlock *rb = p->pages->block;
> uint64_t packet_num = p->packet_num;
> p->flags = 0;
> if (p->sync_needed) {
> @@ -688,8 +710,16 @@ static void *multifd_send_thread(void *opaque)
> }
>
> for (int i = 0; i < p->pages->num; i++) {
> - p->normal[p->normal_num] = p->pages->offset[i];
> - p->normal_num++;
> + uint64_t offset = p->pages->offset[i];
> + if (use_zero_page &&
> + buffer_is_zero(rb->host + offset, p->page_size)) {
> + p->zero[p->zero_num] = offset;
Same here.
> + p->zero_num++;
> + ram_release_page(rb->idstr, offset);
> + } else {
> + p->normal[p->normal_num] = offset;
Same here? (p->normal[i] can also be u32)
> + p->normal_num++;
> + }
> }
>
> if (p->normal_num) {
> @@ -1152,6 +1182,13 @@ static void *multifd_recv_thread(void *opaque)
> }
> }
>
> + for (int i = 0; i < p->zero_num; i++) {
> + void *page = p->host + p->zero[i];
> + if (!buffer_is_zero(page, p->page_size)) {
> + memset(page, 0, p->page_size);
> + }
> + }
> +
> if (sync_needed) {
> qemu_sem_post(&multifd_recv_state->sem_sync);
> qemu_sem_wait(&p->sem_sync);
next prev parent reply other threads:[~2022-09-02 13:37 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-02 6:38 [PATCH v7 00/12] Migration: Transmit and detect zero pages in the multifd threads Juan Quintela
2022-08-02 6:38 ` [PATCH v7 01/12] multifd: Create page_size fields into both MultiFD{Recv, Send}Params Juan Quintela
2022-08-11 8:10 ` [PATCH v7 01/12] multifd: Create page_size fields into both MultiFD{Recv,Send}Params Leonardo Brás
2022-08-13 15:41 ` Juan Quintela
2022-08-02 6:38 ` [PATCH v7 02/12] multifd: Create page_count fields into both MultiFD{Recv, Send}Params Juan Quintela
2022-08-11 8:10 ` [PATCH v7 02/12] multifd: Create page_count fields into both MultiFD{Recv,Send}Params Leonardo Brás
2022-08-02 6:38 ` [PATCH v7 03/12] migration: Export ram_transferred_ram() Juan Quintela
2022-08-11 8:11 ` Leonardo Brás
2022-08-13 15:36 ` Juan Quintela
2022-08-02 6:38 ` [PATCH v7 04/12] multifd: Count the number of bytes sent correctly Juan Quintela
2022-08-11 8:11 ` Leonardo Brás
2022-08-19 9:35 ` Juan Quintela
2022-08-02 6:39 ` [PATCH v7 05/12] migration: Make ram_save_target_page() a pointer Juan Quintela
2022-08-11 8:11 ` Leonardo Brás
2022-08-19 9:51 ` Juan Quintela
2022-08-20 7:14 ` Leonardo Bras Soares Passos
2022-08-22 21:35 ` Juan Quintela
2022-08-02 6:39 ` [PATCH v7 06/12] multifd: Make flags field thread local Juan Quintela
2022-08-11 9:04 ` Leonardo Brás
2022-08-19 10:03 ` Juan Quintela
2022-08-20 7:24 ` Leonardo Bras Soares Passos
2022-08-23 13:00 ` Juan Quintela
2022-08-02 6:39 ` [PATCH v7 07/12] multifd: Prepare to send a packet without the mutex held Juan Quintela
2022-08-11 9:16 ` Leonardo Brás
2022-08-19 11:32 ` Juan Quintela
2022-08-20 7:27 ` Leonardo Bras Soares Passos
2022-08-02 6:39 ` [PATCH v7 08/12] multifd: Add capability to enable/disable zero_page Juan Quintela
2022-08-11 9:29 ` Leonardo Brás
2022-08-19 11:36 ` Juan Quintela
2022-08-02 6:39 ` [PATCH v7 09/12] migration: Export ram_release_page() Juan Quintela
2022-08-11 9:31 ` Leonardo Brás
2022-08-02 6:39 ` [PATCH v7 10/12] multifd: Support for zero pages transmission Juan Quintela
2022-09-02 13:27 ` Leonardo Brás
2022-11-14 12:09 ` Juan Quintela
2022-10-25 9:10 ` chuang xu
2022-11-14 12:10 ` Juan Quintela
2022-08-02 6:39 ` [PATCH v7 11/12] multifd: Zero " Juan Quintela
2022-09-02 13:27 ` Leonardo Brás [this message]
2022-11-14 12:20 ` Juan Quintela
2022-11-14 12:27 ` Juan Quintela
2022-08-02 6:39 ` [PATCH v7 12/12] So we use multifd to transmit zero pages Juan Quintela
2022-09-02 13:27 ` Leonardo Brás
2022-11-14 12:30 ` Juan Quintela
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