Re: What are the first 2 columns in "top"'s memory report for really? Man page doesn't say!
On Tue, Dec 22, 2015 at 02:31:58AM +0800, Tinker wrote: > Hi, on my 4GB RAM machine, top says > > "Memory: Real: 1293M/3786M act/tot Free: 158M Cache: 2079M Swap: 449M/10G" > > All the five first columns vary over time, in particular the first four. > > 3786 + 158 = 3944 is fairly close to 4GB so I guess that's the amount of RAM > that the BIOS (+HW drivers?) actually left usable, so that number makes > sense. AFAIK: tot: memory allocated by kernel act: memory recently accessed, subset of tot. free: memory not allocated tot + free: total memory available cache: pages allocated to buffer (filesystem) cache all memory includes both kernel and memory used by processes. -Otto > > The 158 number is fairly clear also - that's all the RAM that's not in use. > > And the 2079 number should be the total amount of filesystem cache. > > But then what are the first two numbers, and there in particular the second > one?? > > I guess the first one is the total amount of malloc():s (I guess including > the actual malloc structures). > > But the second one makes no sense - 1293 (first column) + 2079 (fourth > column) make 3372 so this number does not only cover malloc:s and the FS > cache then, but there are 414MB of other stuff. Is it that the kernel with > all of its work takes 414MB?? If so that's weird because really the machine > doesn't do a lot. > > The "man" page doesn't say any of this. > > I think it's good to know this, for diagnostic purposes. > > Anyone knows what the second column is for? > > Thanks, > Tinker
Re: What are the first 2 columns in "top"'s memory report for really? Man page doesn't say!
On 2015-12-22 03:32, Otto Moerbeek wrote: On Tue, Dec 22, 2015 at 02:31:58AM +0800, Tinker wrote: Hi, on my 4GB RAM machine, top says "Memory: Real: 1293M/3786M act/tot Free: 158M Cache: 2079M Swap: 449M/10G" All the five first columns vary over time, in particular the first four. 3786 + 158 = 3944 is fairly close to 4GB so I guess that's the amount of RAM that the BIOS (+HW drivers?) actually left usable, so that number makes sense. AFAIK: tot: memory allocated by kernel act: memory recently accessed, subset of tot. free: memory not allocated tot + free: total memory available cache: pages allocated to buffer (filesystem) cache all memory includes both kernel and memory used by processes. Interesting. Okay so mallocs could be a huge part of the "tot" then. Do you have any idea of the definition of "active" here? (As in what makes a given part of "tot" be declared "active" by the OS.) Also what special treatment may the OS give memory that is not "active", swap it to disk??
Re: What are the first 2 columns in "top"'s memory report for really? Man page doesn't say!
On Tue, Dec 22, 2015 at 04:04:55AM +0800, Tinker wrote: > On 2015-12-22 03:32, Otto Moerbeek wrote: > >On Tue, Dec 22, 2015 at 02:31:58AM +0800, Tinker wrote: > > > >>Hi, on my 4GB RAM machine, top says > >> > >>"Memory: Real: 1293M/3786M act/tot Free: 158M Cache: 2079M Swap: > >>449M/10G" > >> > >>All the five first columns vary over time, in particular the first four. > >> > >>3786 + 158 = 3944 is fairly close to 4GB so I guess that's the amount of > >>RAM > >>that the BIOS (+HW drivers?) actually left usable, so that number makes > >>sense. > > > >AFAIK: > > > >tot: memory allocated by kernel > >act: memory recently accessed, subset of tot. > >free: memory not allocated > >tot + free: total memory available > >cache: pages allocated to buffer (filesystem) cache > > > >all memory includes both kernel and memory used by processes. > > Interesting. > > Okay so mallocs could be a huge part of the "tot" then. > > Do you have any idea of the definition of "active" here? > > (As in what makes a given part of "tot" be declared "active" by the OS.) > > Also what special treatment may the OS give memory that is not "active", > swap it to disk?? > Don't know the details how/when pages are marked inactive, but the general ideas is: inactive r/o pages may be reclaimed when pages are needed, inactive (and dirty) r/w pages may be written to disk (for buffers) or swap (other r/w pages) when pages are needed for other things. -Otto
