feat(mm): 添加slab内存分配器 #683

laokengwt · 2024-04-02T09:19:24Z

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dragonosbot · 2024-04-02T09:19:30Z

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fslongjin · 2024-04-02T15:47:10Z

r? @GnoCiYeH

fslongjin · 2024-04-02T15:47:34Z

PR的更改就直接push到原来分支就可以了，不用再开PR哈哈哈哈

laokengwt · 2024-04-02T15:48:31Z

收到

fslongjin · 2024-04-04T04:56:55Z

issue: #523

GnoCiYeH

有些小问题需要修改。请问有测试用例吗，或者说对比加入slab前后的内存分配情况？

kernel/src/mm/allocator/kernel_allocator.rs

GnoCiYeH · 2024-04-04T06:52:28Z

kernel/src/mm/allocator/kernel_allocator.rs

-        return r;
-
-        // self.local_alloc_zeroed(layout, 0)
+        if layout.size() > 2048 || !slab_init_state() {


这里的写法感觉有点冗余，可以精简一下，因为两部分的区别只有一个type不一样而已

GnoCiYeH · 2024-04-04T06:52:42Z

kernel/src/mm/allocator/kernel_allocator.rs

-        );
-
-        return r;
+        if layout.size() > 2048 || !slab_init_state() {


这里与上同理

GnoCiYeH · 2024-04-04T06:52:54Z

kernel/src/mm/allocator/kernel_allocator.rs

-        );
-
-        self.local_dealloc(ptr, layout);
+        if layout.size() > 2048 || !slab_init_state() {


GnoCiYeH · 2024-04-04T06:54:17Z

kernel/src/mm/allocator/slab.rs

-    len: usize,
-    head: Option<&'static mut FreeBlock>,
+// slab初始化状态
+pub(crate) static mut SLABINITSTATE: bool = false;


这里应该使用AtomicBool，避免并发问题

这个不Atomic也行的，因为只会从false变为true. 只要他改的时候，加好compiler_fence，防止编译器的神奇优化。就行了。

GnoCiYeH · 2024-04-04T06:56:41Z

kernel/src/mm/allocator/slab.rs

-        return self.free_block_list.len();
-    }
+// 全局slab分配器
+pub(crate) static SLABALLOCATOR: SpinLock<Option<SlabAllocator>> = SpinLock::new(None);


这个地方感觉SpinLock<Option<SlabAllocator>>不太好，可以使用Option<SpinLock<SlabAllocator>>或者Lazy<SpinLock<SlabAllocator>>。

这个地方感觉SpinLock<Option<SlabAllocator>>不太好，可以使用Option<SpinLock<SlabAllocator>>或者Lazy<SpinLock<SlabAllocator>>。

首先不要用lazy，因为很慢。
然后就是，全局分配器的话，他这里应该是想实现延迟初始化。只要初始化时机控制的正确，就不需要锁，只要unsafe一下就行。

GnoCiYeH · 2024-04-04T07:00:41Z

kernel/src/mm/allocator/kernel_allocator.rs

-            .map(|x| x.as_mut_ptr())
-            .unwrap_or(core::ptr::null_mut());
+        if layout.size() > 2048 || !slab_init_state() {
+            return self


多次使用到了这个判断条件，可以封装成一个内联函数。

laokengwt · 2024-04-05T08:19:03Z

有些小问题需要修改。请问有测试用例吗，或者说对比加入slab前后的内存分配情况？

没有测试用例，但是可以通过make log-monitor在log文件夹中打印出内存分配的log，可以得到其分配方式与原来的buddy分配不同，并且确实是按照slab分配的方式来分配内存的

fslongjin · 2024-04-05T08:17:29Z

kernel/src/mm/allocator/kernel_allocator.rs

@@ -62,21 +62,21 @@ impl KernelAllocator {
 /// 为内核分配器实现LocalAlloc的trait
 impl LocalAlloc for KernelAllocator {
    unsafe fn local_alloc(&self, layout: Layout) -> *mut u8 {
-        if layout.size() > 2048 || !slab_init_state() {
+        if allocator_select_condition(layout) {


函数名不直观，改为layout_use_buddy(xxxxxx)更好。

fslongjin · 2024-04-05T08:19:08Z

kernel/src/mm/allocator/kernel_allocator.rs

-
-            self.local_dealloc(ptr, layout);
+        if allocator_select_condition(layout) {
+            dealloc_debug_log(klog_types::LogSource::Buddy, layout, ptr);


这里存在问题：
在slab初始化之前，分配出去的对象（他们的layout小于等于2048，比如说32字节吧。），但仍然分配了4K出去。在归还的时候，归还了32到slab（而不是归还4k给buddy）

Chiichen

后面可以跑一些现有的负载程序，比如http server，看一下内存占用优化情况(比如减少了百分之多少)，因为这是内核里少有的可以量化的指标了

laokengwt · 2024-04-14T14:07:01Z

@dragonosbot review

fslongjin · 2024-04-15T04:35:10Z

还有另一个问题就是，你下回记得不要在master上面开发哈哈哈

feat(mm): 添加slab内存分配器 --------- Co-authored-by: longjin <[email protected]>

slab

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dragonosbot added the S-等待审查 Status: 等待assignee以及相关方的审查。 label Apr 2, 2024

slab

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dragonosbot assigned GnoCiYeH Apr 2, 2024

GnoCiYeH requested changes Apr 4, 2024

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dragonosbot added S-等待作者修改 Status: 这正在等待作者的一些操作（例如代码更改或更多信息）。 and removed S-等待审查 Status: 等待assignee以及相关方的审查。 labels Apr 4, 2024

修改了部分冗余代码

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fslongjin requested changes Apr 5, 2024

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fslongjin added the A-mm Area: 内存管理子系统 label Apr 6, 2024

Chiichen reviewed Apr 7, 2024

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laokengwt and others added 4 commits April 11, 2024 18:05

Merge branch 'DragonOS-Community:master' into master

aa5aee7

Merge branch 'DragonOS-Community:master' into master

f64a82d

更新slab分配器

e757329

make fmt修改

962be53

Chiichen changed the title ~~添加slab内存分配器~~ feat(mm): 添加slab内存分配器 Apr 14, 2024

添加注释

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fslongjin approved these changes Apr 15, 2024

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fmt

16472ce

fslongjin merged commit ceeb2e9 into DragonOS-Community:master Apr 15, 2024
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BrahmaMantra pushed a commit to BrahmaMantra/DragonOS that referenced this pull request Dec 9, 2024

feat(mm): 添加slab内存分配器 (DragonOS-Community#683)

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feat(mm): 添加slab内存分配器 --------- Co-authored-by: longjin <[email protected]>

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feat(mm): 添加slab内存分配器 #683

feat(mm): 添加slab内存分配器 #683

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feat(mm): 添加slab内存分配器 #683

feat(mm): 添加slab内存分配器 #683

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