“无法分配内存”的原因是什么？除了超出地址空间和内存碎片之外？
问题是，在 Mac OS X 上的 32 位应用程序中，收到错误
malloc: *** mmap(size=49721344) failed (error code=12)
*** error: can't allocate region
*** set a breakpoint in malloc_error_break to debug
参考错误代码位于 sys/errno.h 中：
#define ENOMEM 12 /* Cannot allocate memory */
内存分配模式如下：
- 首先分配近 250MB 的内存
- 分配 6 个 32MB 的块
- 然后27张图像每张都这样处理
- 分配 16MB（图像位图已加载）
- 分配 32MB，处理它，释放这 32MB
- 再次分配32MB，处理它，释放这32MB
- 第 3.1 步中分配的免费 16MB
- 释放步骤 2 中分配的 4 个块（仍使用 2 个块） )
- 步骤 1 中分配的空闲 250MB 块
- 分配各种大小的块，总大小不超过 250MB。在这里，我收到了提到的内存分配错误，
我已经检查过这些内存块都没有泄漏，所以我猜想在任何给定时间使用的内存都保持在 1GB 以下，这应该可以在 32 位系统上访问。
第二个猜测是内存碎片。但我已经检查过步骤 3 中的所有块都重复使用相同的地址。所以我接触的内存不到 1GB - 内存碎片应该不是问题。
现在我完全不知道不分配内存的原因是什么。当我处理少于 27 个图像时，一切正常。以下是步骤 6 之前的 26 个图像的堆命令结果的一部分：
Process 1230: 4 zones
Zone DefaultMallocZone_0x273000: Overall size: 175627KB; 29620 nodes malloced for 68559KB (39% of capacity); largest unused: [0x6f800000-8191KB]
Zone DispatchContinuations_0x292000: Overall size: 4096KB; 1 nodes malloced for 1KB (0% of capacity); largest unused: [0x2600000-1023KB]
Zone QuartzCore_0x884400: Overall size: 232KB; 7039 nodes malloced for 132KB (56% of capacity); largest unused: [0x3778ca0-8KB]
Zone DefaultPurgeableMallocZone_0x27f2000: Overall size: 4KB; 0 nodes malloced for 0KB (0% of capacity); largest unused: [0x3723000-4KB]
All zones: 36660 nodes malloced - 68691KB
对于 27 个图像：
Process 1212: 4 zones
Zone DefaultMallocZone_0x273000: Overall size: 167435KB; 30301 nodes malloced for 68681KB (41% of capacity); largest unused: [0x6ea51000-32372KB]
Zone DispatchContinuations_0x292000: Overall size: 4096KB; 1 nodes malloced for 1KB (0% of capacity); largest unused: [0x500000-1023KB]
Zone QuartzCore_0x106b000: Overall size: 192KB; 5331 nodes malloced for 101KB (52% of capacity); largest unused: [0x37f2f98-8KB]
Zone DefaultPurgeableMallocZone_0x30f8000: Overall size: 4KB; 0 nodes malloced for 0KB (0% of capacity); largest unused: [0x368f000-4KB]
All zones: 35633 nodes malloced - 68782KB
那么“无法分配内存”的其他原因是什么以及如何诊断它们？或者我可能犯了一个错误，排除了上述原因，那么我该如何再次检查它们呢？
The problem is that in a 32-bit application on Mac OS X I receive an error
malloc: *** mmap(size=49721344) failed (error code=12)
*** error: can't allocate region
*** set a breakpoint in malloc_error_break to debug
For the reference error code is in sys/errno.h:
#define ENOMEM 12 /* Cannot allocate memory */
The memory allocation pattern is like this:
- First is allocated nearly 250MB of memory
- Allocate 6 blocks of 32MB
- Then 27 images each handled like this
- Allocate 16MB (image bitmap is loaded)
- Allocate 32MB, process it, free these 32MB
- Again allocate 32MB, process it, free these 32MB
- Free 16MB allocated in step 3.1
- Free 4 blocks allocated in step 2 (2 blocks are still used)
- Free 250MB block allocated in step 1
- Allocate blocks of various size, total size doesn't exceed 250MB. And here I receive the mentioned memory allocation error
I've checked that none of these memory blocks is leaked, so I guess used memory at any given time stays below 1GB, which should be accessible on 32-bit system.
The second guess was memory fragmentation. But I've checked that all block in step 3 reuse same addresses. So I touch less than 1GB of memory - memory fragmentation should not be an issue.
Now I am completely lost what can be a reason for not allocating memory. Also everything works OK when I process less than 27 images. Here is part of heap command result before step 6 for 26 images:
Process 1230: 4 zones
Zone DefaultMallocZone_0x273000: Overall size: 175627KB; 29620 nodes malloced for 68559KB (39% of capacity); largest unused: [0x6f800000-8191KB]
Zone DispatchContinuations_0x292000: Overall size: 4096KB; 1 nodes malloced for 1KB (0% of capacity); largest unused: [0x2600000-1023KB]
Zone QuartzCore_0x884400: Overall size: 232KB; 7039 nodes malloced for 132KB (56% of capacity); largest unused: [0x3778ca0-8KB]
Zone DefaultPurgeableMallocZone_0x27f2000: Overall size: 4KB; 0 nodes malloced for 0KB (0% of capacity); largest unused: [0x3723000-4KB]
All zones: 36660 nodes malloced - 68691KB
And for 27 images:
Process 1212: 4 zones
Zone DefaultMallocZone_0x273000: Overall size: 167435KB; 30301 nodes malloced for 68681KB (41% of capacity); largest unused: [0x6ea51000-32372KB]
Zone DispatchContinuations_0x292000: Overall size: 4096KB; 1 nodes malloced for 1KB (0% of capacity); largest unused: [0x500000-1023KB]
Zone QuartzCore_0x106b000: Overall size: 192KB; 5331 nodes malloced for 101KB (52% of capacity); largest unused: [0x37f2f98-8KB]
Zone DefaultPurgeableMallocZone_0x30f8000: Overall size: 4KB; 0 nodes malloced for 0KB (0% of capacity); largest unused: [0x368f000-4KB]
All zones: 35633 nodes malloced - 68782KB
So what are other reasons for "Cannot allocate memory" and how can I diagnose them? Or probably I made a mistake ruling out mentioned reasons, then how can I check them again?
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结果我在检查地址空间是否耗尽时犯了一个错误。我应该使用
vmmap，而不是使用heap命令。vmmap显示大部分内存被映射到内存的图像使用。Turned out I've made a mistake checking that address space is not exhausted. Instead of using
heapcommand I should have usedvmmap.vmmaprevealed that most of the memory is used by images mapped into the memory.