On Mon, Dec 16, 2013 at 08:31:46AM +0100, Holger Winkelmann [TP] wrote: > Hi, > > > > > Is there any particular reason? I think thresold for runtime journal > > > > size can lower much because in initramfs it's not supposed to have much > > > > logs. > > > First, there are some data strcutures which are allocated when the file > > > is created, and if the file was very small, relatively more space would > > > wasted. Second, repeated fields are not stored, just referenced, so things > > > become more efficient when the file is not too small. But neither is > > > fundamental reason, and with some tweaking the journal could be made > > > to work much smaller files. > > > > I understand. These are really good points when logs are relatively > > large, ie. the journal is stored on a real disk. > > > > However when it's in initramfs context, journal is stored in tmpfs which > > is using the real memory resource as it's backend. 4 MB seems a little > > bit overkill especially when memory is quite limited case, like kdump. > > To be more specific, I think 512 KB or 1 MB is a fairly large enough > > nubmer when journal is stored to a volatile backend. > > We totally agree that a minimum size must be below 1MB either on flash or > ramfs for embedded devices. otherwise you end up with two solutions for > smaller > and bigger devices. Is there any reference about the overhead if you use > smaller > file size? Is there technical limitation for a minimum size? No, there's no real technical limitation. Except some hero should go through src/jounal/journal-file.c and adjust all the constants that they also work with very small files.
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