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Allocate DNS send buffers using dedicated per-worker memory arenas

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This commit ensures that memory allocations related to DNS send
buffers are routed through dedicated per-worker memory arenas in order
to decrease memory usage on high load caused by TCP-based DNS
transports.

We do that by following jemalloc developers suggestions:

https://github.com/jemalloc/jemalloc/issues/2483#issuecomment-1639019699
https://github.com/jemalloc/jemalloc/issues/2483#issuecomment-1698173849
(cherry picked from commit 01cc7edcca)
This commit is contained in:
Artem Boldariev
2023-08-10 23:08:25 +03:00
committed by Ondřej Surý
parent f5cb14265f
commit 1cc17f797e
3 changed files with 75 additions and 8 deletions
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77
lib/ns/client.c
View File

@@ -346,7 +346,7 @@ client_allocsendbuf(ns_client_t *client, isc_buffer_t *buffer,
if (TCP_CLIENT(client)) {
INSIST(client->tcpbuf == NULL);
client->tcpbuf = isc_mem_get(client->mctx,
client->tcpbuf = isc_mem_get(client->manager->send_mctx,
NS_CLIENT_TCP_BUFFER_SIZE);
client->tcpbuf_size = NS_CLIENT_TCP_BUFFER_SIZE;
data = client->tcpbuf;
@@ -383,7 +383,7 @@ client_sendpkg(ns_client_t *client, isc_buffer_t *buffer) {
if (isc_buffer_base(buffer) == client->tcpbuf) {
size_t used = isc_buffer_usedlength(buffer);
client->tcpbuf = isc_mem_reget(client->manager->mctx,
client->tcpbuf = isc_mem_reget(client->manager->send_mctx,
client->tcpbuf,
client->tcpbuf_size, used);
client->tcpbuf_size = used;
@@ -461,7 +461,8 @@ ns_client_sendraw(ns_client_t *client, dns_message_t *message) {
return;
done:
if (client->tcpbuf != NULL) {
isc_mem_put(client->mctx, client->tcpbuf, client->tcpbuf_size);
isc_mem_put(client->manager->send_mctx, client->tcpbuf,
client->tcpbuf_size);
}
ns_client_drop(client, result);
@@ -745,7 +746,8 @@ renderend:
cleanup:
if (client->tcpbuf != NULL) {
isc_mem_put(client->mctx, client->tcpbuf, client->tcpbuf_size);
isc_mem_put(client->manager->send_mctx, client->tcpbuf,
client->tcpbuf_size);
}
if (cleanup_cctx) {
@@ -1627,7 +1629,8 @@ ns__client_reset_cb(void *client0) {
ns_client_endrequest(client);
if (client->tcpbuf != NULL) {
isc_mem_put(client->mctx, client->tcpbuf, client->tcpbuf_size);
isc_mem_put(client->manager->send_mctx, client->tcpbuf,
client->tcpbuf_size);
}
if (client->keytag != NULL) {
@@ -1658,7 +1661,8 @@ ns__client_put_cb(void *client0) {
client->magic = 0;
client->shuttingdown = true;
isc_mem_put(client->mctx, client->sendbuf, NS_CLIENT_SEND_BUFFER_SIZE);
isc_mem_put(client->manager->send_mctx, client->sendbuf,
NS_CLIENT_SEND_BUFFER_SIZE);
if (client->opt != NULL) {
INSIST(dns_rdataset_isassociated(client->opt));
dns_rdataset_disassociate(client->opt);
@@ -2340,7 +2344,7 @@ ns__client_setup(ns_client_t *client, ns_clientmgr_t *mgr, bool new) {
dns_message_create(client->mctx, DNS_MESSAGE_INTENTPARSE,
&client->message);
client->sendbuf = isc_mem_get(client->mctx,
client->sendbuf = isc_mem_get(client->manager->send_mctx,
NS_CLIENT_SEND_BUFFER_SIZE);
/*
* Set magic earlier than usual because ns_query_init()
@@ -2399,7 +2403,7 @@ ns__client_setup(ns_client_t *client, ns_clientmgr_t *mgr, bool new) {
cleanup:
if (client->sendbuf != NULL) {
isc_mem_put(client->mctx, client->sendbuf,
isc_mem_put(client->manager->send_mctx, client->sendbuf,
NS_CLIENT_SEND_BUFFER_SIZE);
}
@@ -2475,6 +2479,8 @@ clientmgr_destroy(ns_clientmgr_t *manager) {
isc_task_detach(&manager->task);
ns_server_detach(&manager->sctx);
isc_mem_detach(&manager->send_mctx);
isc_mem_putanddetach(&manager->mctx, manager, sizeof(*manager));
}
@@ -2511,6 +2517,61 @@ ns_clientmgr_create(ns_server_t *sctx, isc_taskmgr_t *taskmgr,
ISC_LIST_INIT(manager->recursing);
/*
* We create specialised per-worker memory context specifically
* dedicated and tuned for allocating send buffers as it is a very
* common operation. Not doing so may result in excessive memory
* use in certain workloads.
*
* Please see this thread for more details:
*
* https://github.com/jemalloc/jemalloc/issues/2483
*
* In particular, this information from the jemalloc developers is
* of the most interest:
*
* https://github.com/jemalloc/jemalloc/issues/2483#issuecomment-1639019699
* https://github.com/jemalloc/jemalloc/issues/2483#issuecomment-1698173849
*
* In essence, we use the following memory management strategy:
*
* 1. We use a per-worker memory arena for send buffers memory
* allocation to reduce lock contention (In reality, we create a
* per-client manager arena, but we have one client manager per
* worker).
*
* 2. The automatically created arenas settings remain unchanged
* and may be controlled by users (e.g. by setting the
* "MALLOC_CONF" variable).
*
* 3. We attune the arenas to not use dirty pages cache as the
* cache would have a poor reuse rate, and that is known to
* significantly contribute to excessive memory use.
*
* 4. There is no strict need for the dirty cache, as there is a
* per arena bin for each allocation size, so because we initially
* allocate strictly 64K per send buffer (enough for a DNS
* message), allocations would get directed to one bin (an "object
* pool" or a "slab") maintained within an arena. That is, there
* is an object pool already, specifically to optimise for the
* case of frequent allocations of objects of the given size. The
* object pool should suffice our needs, as we will end up
* recycling the objects from there without the need to back it by
* an additional layer of dirty pages cache. The dirty pages cache
* would have worked better in the case when there are more
* allocation bins involved due to a higher reuse rate (the case
* of a more "generic" memory management).
*/
isc_mem_create_arena(&manager->send_mctx);
isc_mem_setname(manager->send_mctx, "sendbufs");
(void)isc_mem_arena_set_dirty_decay_ms(manager->send_mctx, 0);
/*
* Disable muzzy pages cache too, as versions < 5.2.0 have it
* enabled by default. The muzzy pages cache goes right below the
* dirty pages cache and backs it.
*/
(void)isc_mem_arena_set_muzzy_decay_ms(manager->send_mctx, 0);
manager->magic = MANAGER_MAGIC;
MTRACE("create");

1
lib/ns/include/ns/client.h
View File

@@ -144,6 +144,7 @@ struct ns_clientmgr {
unsigned int magic;
isc_mem_t *mctx;
isc_mem_t *send_mctx;
ns_server_t *sctx;
isc_taskmgr_t *taskmgr;
isc_timermgr_t *timermgr;

5
lib/ns/server.c
View File

@@ -49,6 +49,11 @@ ns_server_create(isc_mem_t *mctx, ns_matchview_t matchingview,
isc_mem_attach(mctx, &sctx->mctx);
/*
* See here for more details:
* https://github.com/jemalloc/jemalloc/issues/2483
*/
isc_refcount_init(&sctx->references, 1);
isc_quota_init(&sctx->xfroutquota, 10);