内存 – Linux巨大的页面使用会计

我已经配置了用于 Java的巨大页面,虽然我对/ proc / meminfo中的会计有疑问,但它似乎运行良好.为了显示

# grep HugePages /proc/meminfo 
AnonHugePages:    274432 kB
HugePages_Total:    1008
HugePages_Free:      596
HugePages_Rsvd:      594
HugePages_Surp:        0

我的问题涉及“免费”和“Rsvd”号码 – 为什么它们不加起来总计1008？他们实际上加起来是1190.我在这里不理解什么？

解决方法

这是因为HugePages_rsvd基本上是从HugePages_Free中读取的.意思是,在596个免费的大页面中,有594个已被某些应用程序保留使用.那就是内核承诺这些594个大页面可用于该应用程序.

如果现在有3个大页面的请求,那么它将失败,因为只有2个可用于保留.将其视为malloc()调用,当您保留内存虚拟页面以考虑进程的VSZ时,但当进程实际使用它们时,它将成为进程的RSZ(运行集).

由于大页面总是驻留在主内存上,当应用程序请求它们时,内核会从空闲池中减少它并增加Rsvd计数器.

这是来自内核源代码. https://www.kernel.org/doc/Documentation/vm/hugetlbpage.txt

where:
HugePages_Total is the size of the pool of huge pages.
HugePages_Free  is the number of huge pages in the pool that are not yet
                allocated.
HugePages_Rsvd  is short for "reserved," and is the number of huge pages for
                which a commitment to allocate from the pool has been made,but no allocation has yet been made.  Reserved huge pages
                guarantee that an application will be able to allocate a
                huge page from the pool of huge pages at fault time.
HugePages_Surp  is short for "surplus," and is the number of huge pages in
                the pool above the value in /proc/sys/vm/nr_hugepages. The
                maximum number of surplus huge pages is controlled by
                /proc/sys/vm/nr_overcommit_hugepages.