Skip to content

sharp: apply SHARP_COLLNET_OVERLAP_AG env profile #184

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
bureddy merged 1 commit into from
Jan 12, 2026
Merged

sharp: apply SHARP_COLLNET_OVERLAP_AG env profile #184

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
28 changes: 26 additions & 2 deletions src/sharp_plugin.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -8,12 +8,12 @@

#include <pthread.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/time.h>
#include <unistd.h>
#include <assert.h>
#include <string.h>

#include "config.h"
#include "core.h"
Expand Down Expand Up @@ -56,6 +56,28 @@ enum ncclSharpRequestType {
NCCL_SHARP_REQ_IFLUSH,
};

static void ncclSharpSetEnv(const char* name, const char* value) {
/* We explicitly want the plugin profile to win over existing env vars. */
setenv(name, value, 1);
}

static void ncclSharpApplyLibEnvProfile(void) {
const char* overlapAgEnv = getenv("SHARP_COLLNET_OVERLAP_AG");
/* Only apply a profile if Megatron explicitly requests it. */
if (overlapAgEnv == NULL) return;

const int overlapAg = (strcmp(overlapAgEnv, "1") == 0);
if (overlapAg) {
/* For allgather overlap (multicast path) */
ncclSharpSetEnv("SHARP_COLL_ENABLE_MCAST", "1");
ncclSharpSetEnv("SHARP_COLL_ENABLE_SAT", "0");
} else {
/* For reduce-scatter (non-overlap default path) */
ncclSharpSetEnv("SHARP_COLL_ENABLE_MCAST", "0");
ncclSharpSetEnv("SHARP_COLL_ENABLE_SAT", "1");
}
}

struct ncclSharpRequest {
int requestType;
void *sharpRequest;
Expand Down Expand Up @@ -220,12 +242,14 @@ ncclResult_t ncclSharpInit(void **ctx, uint64_t commId, ncclDebugLogger_t logFun
gettimeofday(&tval, NULL);
srand((int) tval.tv_usec);

/* set SHARP COLL library default for plugin */
setenv("SHARP_COLL_ENABLE_SAT", "1", 0);
setenv("SHARP_COLL_NUM_COLL_GROUP_RESOURCE_ALLOC_THRESHOLD", "0", 0);
setenv("SHARP_COLL_LOCK_ON_COMM_INIT", "1", 0);
setenv("SHARP_COLL_LOG_LEVEL", "3", 0);

/* Apply Megatron-driven env profile (only if SHARP_COLLNET_OVERLAP_AG is set) */
ncclSharpApplyLibEnvProfile();

if (ncclParamSharpDisableAG()) {
INFO(NCCL_NET, "Disabled SHARP Allgather");
ncclCollNetPlugin_v10.iallgather = NULL;
Expand Down
Loading