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Avoid segmented shared_alloc_shm.c allocation to support OPcache JIT on Solaris #20719

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Avoid segmented shared_alloc_shm.c allocation to support OPcache JIT on Solaris #20719

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d2ca471
Increase SEG_ALLOC_SIZE_MAX to 64MB to support OPcache JIT on Solaris
psumbera Dec 16, 2025
d29a4a9
Improve shared_alloc_shm.c strategy
iluuu1994 Feb 4, 2026
deaf7c8
Fix comment
iluuu1994 Feb 4, 2026
8bc4209
Use SEG_ALLOC_SIZE_MIN instead of hard-coded start value
iluuu1994 Feb 5, 2026
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43 changes: 22 additions & 21 deletions ext/opcache/shared_alloc_shm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,6 @@
# define MIN(x, y) ((x) > (y)? (y) : (x))
#endif

#define SEG_ALLOC_SIZE_MAX 32*1024*1024
#define SEG_ALLOC_SIZE_MIN 2*1024*1024

typedef struct {
Expand All @@ -53,36 +52,38 @@ typedef struct {
static int create_segments(size_t requested_size, zend_shared_segment_shm ***shared_segments_p, int *shared_segments_count, const char **error_in)
{
int i;
size_t allocate_size = 0, remaining_bytes = requested_size, seg_allocate_size;
size_t allocate_size = 0, remaining_bytes, seg_allocate_size;
int first_segment_id = -1;
key_t first_segment_key = -1;
struct shmid_ds sds;
int shmget_flags;
zend_shared_segment_shm *shared_segments;

seg_allocate_size = SEG_ALLOC_SIZE_MAX;
/* determine segment size we _really_ need:
* no more than to include requested_size
*/
while (requested_size * 2 <= seg_allocate_size && seg_allocate_size > SEG_ALLOC_SIZE_MIN) {
seg_allocate_size >>= 1;
}

shmget_flags = IPC_CREAT|SHM_R|SHM_W|IPC_EXCL;

/* try allocating this much, if not - try shrinking */
while (seg_allocate_size >= SEG_ALLOC_SIZE_MIN) {
allocate_size = MIN(requested_size, seg_allocate_size);
first_segment_id = shmget(first_segment_key, allocate_size, shmget_flags);
if (first_segment_id != -1) {
break;
/* Try contiguous allocation first. */
seg_allocate_size = requested_size;
first_segment_id = shmget(first_segment_key, seg_allocate_size, shmget_flags);
if (UNEXPECTED(first_segment_id == -1)) {
/* Search for biggest n^2 < requested_size. */
seg_allocate_size = SEG_ALLOC_SIZE_MIN;
while (seg_allocate_size < requested_size / 2) {
seg_allocate_size *= 2;
}
seg_allocate_size >>= 1; /* shrink the allocated block */
}

if (first_segment_id == -1) {
*error_in = "shmget";
return ALLOC_FAILURE;
/* try allocating this much, if not - try shrinking */
while (seg_allocate_size >= SEG_ALLOC_SIZE_MIN) {
first_segment_id = shmget(first_segment_key, seg_allocate_size, shmget_flags);
if (first_segment_id != -1) {
break;
}
seg_allocate_size >>= 1; /* shrink the allocated block */
}

if (first_segment_id == -1) {
*error_in = "shmget";
return ALLOC_FAILURE;
}
}

*shared_segments_count = ((requested_size - 1) / seg_allocate_size) + 1;
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