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
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=339599
@ -504,6 +504,9 @@ bt_insfree(vmem_t *vm, bt_t *bt)
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/*
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* Import from the arena into the quantum cache in UMA.
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*
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* We use VMEM_ADDR_QCACHE_MIN instead of 0: uma_zalloc() returns 0 to indicate
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* failure, so UMA can't be used to cache a resource with value 0.
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*/
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static int
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qc_import(void *arg, void **store, int cnt, int domain, int flags)
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@ -512,19 +515,16 @@ qc_import(void *arg, void **store, int cnt, int domain, int flags)
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vmem_addr_t addr;
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int i;
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KASSERT((flags & M_WAITOK) == 0, ("blocking allocation"));
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qc = arg;
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if ((flags & VMEM_FITMASK) == 0)
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flags |= M_BESTFIT;
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for (i = 0; i < cnt; i++) {
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if (vmem_xalloc(qc->qc_vmem, qc->qc_size, 0, 0, 0,
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VMEM_ADDR_MIN, VMEM_ADDR_MAX, flags, &addr) != 0)
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VMEM_ADDR_QCACHE_MIN, VMEM_ADDR_MAX, flags, &addr) != 0)
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break;
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store[i] = (void *)addr;
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/* Only guarantee one allocation. */
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flags &= ~M_WAITOK;
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flags |= M_NOWAIT;
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}
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return i;
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return (i);
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}
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/*
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@ -1123,15 +1123,20 @@ vmem_alloc(vmem_t *vm, vmem_size_t size, int flags, vmem_addr_t *addrp)
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WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "vmem_alloc");
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if (size <= vm->vm_qcache_max) {
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/*
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* Resource 0 cannot be cached, so avoid a blocking allocation
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* in qc_import() and give the vmem_xalloc() call below a chance
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* to return 0.
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*/
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qc = &vm->vm_qcache[(size - 1) >> vm->vm_quantum_shift];
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*addrp = (vmem_addr_t)uma_zalloc(qc->qc_cache, flags);
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if (*addrp == 0)
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return (ENOMEM);
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return (0);
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*addrp = (vmem_addr_t)uma_zalloc(qc->qc_cache,
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(flags & ~M_WAITOK) | M_NOWAIT);
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if (__predict_true(*addrp != 0))
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return (0);
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}
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return vmem_xalloc(vm, size, 0, 0, 0, VMEM_ADDR_MIN, VMEM_ADDR_MAX,
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flags, addrp);
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return (vmem_xalloc(vm, size, 0, 0, 0, VMEM_ADDR_MIN, VMEM_ADDR_MAX,
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flags, addrp));
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}
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int
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@ -1263,7 +1268,8 @@ vmem_free(vmem_t *vm, vmem_addr_t addr, vmem_size_t size)
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qcache_t *qc;
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MPASS(size > 0);
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if (size <= vm->vm_qcache_max) {
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if (size <= vm->vm_qcache_max &&
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__predict_true(addr >= VMEM_ADDR_QCACHE_MIN)) {
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qc = &vm->vm_qcache[(size - 1) >> vm->vm_quantum_shift];
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uma_zfree(qc->qc_cache, (void *)addr);
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} else
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@ -41,8 +41,9 @@ typedef struct vmem vmem_t;
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typedef uintptr_t vmem_addr_t;
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typedef size_t vmem_size_t;
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#define VMEM_ADDR_MIN 0
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#define VMEM_ADDR_MAX (~(vmem_addr_t)0)
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#define VMEM_ADDR_MIN 0
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#define VMEM_ADDR_QCACHE_MIN 1
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#define VMEM_ADDR_MAX (~(vmem_addr_t)0)
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typedef int (vmem_import_t)(void *, vmem_size_t, int, vmem_addr_t *);
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typedef void (vmem_release_t)(void *, vmem_addr_t, vmem_size_t);
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