[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] How much memory does a domain REALLY use...
Apologies if this has been discussed before, but I've been trying to work out just how much memory domains consume (so as to be able to provision memory properly) - this all started when I noticed that a system running JUST my 768MB Dom0 was actually using about 890MB according to xenstat - an extra 122MB seemed a little extreme to me so I went digging; I think I've found something over half so far but I'm not sure about the remaining so I was hoping folks could educate me... Here's what I think I've found (all this is i386, 32-bit PAE...): First, from the domain/dma heap zones, in addition to the actual domain memory allocated with alloc_chunk() in 2MB pieces: . First, the biggie -- swiotlb; if I'm not mistaken, this allocates 64MB from the domain heap (in addition to the 64MB of low memory in the domain itself). Allocated with xen_create_contiguous_region in 256KB chunks. . paging_init() allocates the m2p translation table -- 2MB . The Linux dma_alloc_coherent() routine also calls xen_create_contiguous_region -- each call to this routine will allocate a minimum of one page from the domain heap -- every single driver that does DMA will do this, so there is the possibility of some significant allocations due to DMA buffers. I'm wondering if this comprises the remainder of the 122MB I see... . There are a few other single page allocations but nothing huge Then, from the Xen heap zone a bunch of small stuff: . 128KB for console debug trace (debugtrace_init) . 16KB for serial tx buffer . 16KB for page directory pages (arch_domain_create) . 16KB for stack per VCPU (do_boot_cpu in smpboot) . 16KB per grant table (one per domain - _grant_table_create) . 4KB for grant table references (can grow to 128KB - __gnttab_map_grant_ref) . max of 128KB for xenoprofile buffer space - presumably zero until I actually start profiling. So - I've found about 69MB for sure, plus an unknown quantity of DMA common buffer allocations - still seems a bit shy of the 122MB I see... all thoughts welcome... Thanks, Simon _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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