Re: [B.A.T.M.A.N.] [PATCH 0/2] alfred: Use bitmap to store dataset change events

[Simon Wunderlich <sw@simonwunderlich.de>]

[-- Attachment #1: Type: text/plain, Size: 1842 bytes --]

On Monday, July 24, 2017 11:18:09 PM CEST Sven Eckelmann wrote:
> Hi,
> 
> the --update-command implementation looked quite memory inefficient to me
> and I have therefore replaced it using a simple bit map which stores in
> BIT(i)
> when datatype I was modified. Here from the second patch:
> > The implementation for --update-command uses a double linked list to store
> > the detected modifications of datasets. This implementation requires 24
> > bytes (1 byte data type, 7 bytes padding, 16 bytes linked list pointers)
> > on
> > amd64 for each element of the list. Each modified dataset type requires an
> > own list item. Each list item is allocated using malloc and therefore
> > additional overhead for the libc allocator information has also to be
> > stored next to it. The list head uses a similar amount of memory (16 byte
> > list pointers, 2 byte counter, 6 byte padding) but doesn't require
> > additional allocations.
> > 
> > The list based implementation provides information about modified dataset
> > type and the order in which these modifications were detected. But the
> > latter is not actually required fr --update-command and can therefore be
> > omitted.
> > 
> > A simple 256 bit wide storage element (32 bytes) is enough to keep the
> > required information when only the detected modified data types have to be
> > registered. BIT(i) is either 1 when dataset type i was modified or 0 when
> > no modification was detected. This removes the (de)allocation CPU + memory
> > overhead and avoids list searches when adding newly detected
> > modifications.
> 
> The bitops.h file is used to implement the bit operations and keep the
> details away from the server code. I've reduced the size of the header file
> a little bit because most of it was not used by alfred.

Thanks, applied this series

Cheers,
    Simon

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 833 bytes --]