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author | Mark Johnston <markj@FreeBSD.org> | 2018-10-22 16:16:42 +0000 |
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committer | Mark Johnston <markj@FreeBSD.org> | 2018-10-22 16:16:42 +0000 |
commit | 21744c825f73fc2fa3ad2f037f40839d1d3a3331 (patch) | |
tree | dc7202ebc39e5d23c7dcfb8e3a8e4c337476fe23 | |
parent | d3a4b0dabcd31c0c8a5bf049be688897e49489a0 (diff) | |
download | src-21744c825f73fc2fa3ad2f037f40839d1d3a3331.tar.gz src-21744c825f73fc2fa3ad2f037f40839d1d3a3331.zip |
Don't import 0 into vmem quantum caches.
vmem uses UMA cache zones to implement the quantum cache. Since
uma_zalloc() returns 0 (NULL) to signal an allocation failure, UMA
should not be used to cache resource 0. Fix this by ensuring that 0 is
never cached in UMA in the first place, and by modifying vmem_alloc()
to fall back to a search of the free lists if the cache is depleted,
rather than blocking in qc_import().
Reported by and discussed with: Brett Gutstein <bgutstein@rice.edu>
Reviewed by: alc
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D17483
Notes
Notes:
svn path=/head/; revision=339599
-rw-r--r-- | sys/kern/subr_vmem.c | 34 | ||||
-rw-r--r-- | sys/sys/vmem.h | 5 |
2 files changed, 23 insertions, 16 deletions
diff --git a/sys/kern/subr_vmem.c b/sys/kern/subr_vmem.c index 8529266f381c..c93460f96da7 100644 --- a/sys/kern/subr_vmem.c +++ b/sys/kern/subr_vmem.c @@ -504,6 +504,9 @@ bt_insfree(vmem_t *vm, bt_t *bt) /* * Import from the arena into the quantum cache in UMA. + * + * We use VMEM_ADDR_QCACHE_MIN instead of 0: uma_zalloc() returns 0 to indicate + * failure, so UMA can't be used to cache a resource with value 0. */ static int qc_import(void *arg, void **store, int cnt, int domain, int flags) @@ -512,19 +515,16 @@ qc_import(void *arg, void **store, int cnt, int domain, int flags) vmem_addr_t addr; int i; + KASSERT((flags & M_WAITOK) == 0, ("blocking allocation")); + qc = arg; - if ((flags & VMEM_FITMASK) == 0) - flags |= M_BESTFIT; for (i = 0; i < cnt; i++) { if (vmem_xalloc(qc->qc_vmem, qc->qc_size, 0, 0, 0, - VMEM_ADDR_MIN, VMEM_ADDR_MAX, flags, &addr) != 0) + VMEM_ADDR_QCACHE_MIN, VMEM_ADDR_MAX, flags, &addr) != 0) break; store[i] = (void *)addr; - /* Only guarantee one allocation. */ - flags &= ~M_WAITOK; - flags |= M_NOWAIT; } - return i; + return (i); } /* @@ -1123,15 +1123,20 @@ vmem_alloc(vmem_t *vm, vmem_size_t size, int flags, vmem_addr_t *addrp) WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "vmem_alloc"); if (size <= vm->vm_qcache_max) { + /* + * Resource 0 cannot be cached, so avoid a blocking allocation + * in qc_import() and give the vmem_xalloc() call below a chance + * to return 0. + */ qc = &vm->vm_qcache[(size - 1) >> vm->vm_quantum_shift]; - *addrp = (vmem_addr_t)uma_zalloc(qc->qc_cache, flags); - if (*addrp == 0) - return (ENOMEM); - return (0); + *addrp = (vmem_addr_t)uma_zalloc(qc->qc_cache, + (flags & ~M_WAITOK) | M_NOWAIT); + if (__predict_true(*addrp != 0)) + return (0); } - return vmem_xalloc(vm, size, 0, 0, 0, VMEM_ADDR_MIN, VMEM_ADDR_MAX, - flags, addrp); + return (vmem_xalloc(vm, size, 0, 0, 0, VMEM_ADDR_MIN, VMEM_ADDR_MAX, + flags, addrp)); } int @@ -1263,7 +1268,8 @@ vmem_free(vmem_t *vm, vmem_addr_t addr, vmem_size_t size) qcache_t *qc; MPASS(size > 0); - if (size <= vm->vm_qcache_max) { + if (size <= vm->vm_qcache_max && + __predict_true(addr >= VMEM_ADDR_QCACHE_MIN)) { qc = &vm->vm_qcache[(size - 1) >> vm->vm_quantum_shift]; uma_zfree(qc->qc_cache, (void *)addr); } else diff --git a/sys/sys/vmem.h b/sys/sys/vmem.h index e9dc54d154cb..e74d1e3fe803 100644 --- a/sys/sys/vmem.h +++ b/sys/sys/vmem.h @@ -41,8 +41,9 @@ typedef struct vmem vmem_t; typedef uintptr_t vmem_addr_t; typedef size_t vmem_size_t; -#define VMEM_ADDR_MIN 0 -#define VMEM_ADDR_MAX (~(vmem_addr_t)0) +#define VMEM_ADDR_MIN 0 +#define VMEM_ADDR_QCACHE_MIN 1 +#define VMEM_ADDR_MAX (~(vmem_addr_t)0) typedef int (vmem_import_t)(void *, vmem_size_t, int, vmem_addr_t *); typedef void (vmem_release_t)(void *, vmem_addr_t, vmem_size_t); |